Answers and Analysis

1. Section 503.1 - All equipment that produces dust must be interlocked.

2. Section 505.1 - The building or fire code determines when ventilation equipment is required.

3. Section 503.1 - Yes. A planer is considered dust-producing equipment.

No. Domestic range vents and domestic dryer vents do not require a minimum clearance to combustibles unless specifically required by the manufacturer’s installation instructions. It should be noted that there is a 1 inch minimum clearance requirement between an exhaust duct and shaft serving a cooking appliance equipped with an open-top broiler per Section 920.0 (2003/2006).

Commercial dryer exhaust meets the definition of environmental air. The termination for commercial dryers must be in compliance with Section 504.5 (2003/2006/2009/2012) or in accordance with the listing and the manufacturer’s installation instructions, whichever is more restrictive. Section 504.5 requires that environmental air duct exhaust terminate a minimum of 3 feet from property lines and openings into buildings.

Yes, exhaust ducts are prohibited from penetrating any duct or plenum.

Yes, Sections 504.1 (Environmental Air) and 505.1 (Product Conveying Systems) clearly states that exhaust ducts shall not extend into or through ducts and plenums, regardless if the system is under positive or negative pressure.

1. No. A Class 1 exhaust gas duct is classified as a product-conveying duct which is specifically prohibited from extending through ducts and plenums per Section 505.1 (2003/2006/2009/2012). In addition, Section 504.1 prohibits environmental air ducts from extending through ducts and plenums.

2. See answer #1.

3. No

Yes. Section 602.1 refers you to Chapter 5 (2003/2006/2009) for limitations on environmental air systems exhaust ducts extending into or through ducts or plenums.

Section 504.1 does not distinguish between positive and negative pressure in this regard. If a duct system were to become disconnected at or near the source of contaminants, the contaminant could be drawn into the return air plenum and recirculated.

No. The code does not specify where the back-draft damper is to be installed. It only states that a back-draft damper is required.

No. Residential kitchen exhaust is defined as environmental air. There are no requirements specific to environmental air for kitchen exhaust to be mechanically ventilated. If mechanical exhaust is provided, it must be installed per Section 504.2.

No. Sections 504.3.1 and 504.1 (2003/2006/2009/2012) of the UMC both state that exhaust ducts shall be equipped with back-draft dampers.

No, the code requires that a minimum 4 inch diameter duct of approved material shall be installed. The code’s intent is to limit the clothes dryer length to 14 feet unless otherwise permitted or required by the dryer manufacturer’s installation instructions. The vent length restriction is established to help ensure that it will not exceed the maximum allowable length for all available dryers. Typically, the dryer is supplied by the owner and is not installed at time of rough-in inspection.

The UMC does not specifically allow ventless or ductless clothes dryers. All dryer exhaust ducts shall terminate on the outside of the building unless approved by the AHJ as an alternate method.

No. The term “closet” as used in Section 504.3.2, is referring to a space designed specifically for a clothes dryer. These compartments are typically large enough to accommodate a washer/dryer only and are equipped with doors. If the space housing the dryer freely communicates with the laundry room, the laundry room may be used to determine the requirement for make-up air.

No. The language in Sections 504.3.1 and 504.3.2.1 is prescriptive because of the nature of the exhaust content, thus the restriction about screening and the use of connectors (screws) that would obstruct the flow. The understanding is that a lint buildup could occur. Section 504.0 is referenced for direction on the general provisions that say, among other things, “ducts should be substantially airtight” and then refers you to Chapter 6. Section 602.4 (2003/2006/2009) says, “Joints of duct systems shall be made substantially airtight by the means of tapes, mastics, gasketing, or other means.” The committee sees these code sections as allowing quite a range of materials for sealing dryer exhaust ducts. Metal tape is certainly an option, but it would not be required. Careful examination of the manufacturer’s instructions and listings of its sealing products would indicate those suitable for the prolonged heat of a dryer exhaust.

1. Listed or not, air duct connectors are only approved for use with domestic clothes dryers (reference Section 504.3.2.1, Exception).They may be installed between the domestic clothes dryer and the moisture exhaust duct.

2. Yes, but the electric water heater and wiring must be listed for plenum use.

No, 3 feet from building openings is the correct minimum spacing per Section 504.5.

No. Section 504.5, “Termination of Environmental Air Ducts” states, “Environmental air duct exhaust shall terminate a minimum of 3 feet from property line and 3 feet from openings into the building.” The manufacturer’s installation instructions must also be referred to ensure all of their requirements for termination are complied with.

Commercial dryer exhaust meets the definition of environmental air. The termination for commercial dryers must be in compliance with Section 504.5 or in accordance with the listing and the manufacturer’s installation instructions, whichever is more restrictive. Section 504.5 requires that environmental air duct exhaust terminate a minimum of 3 feet from property lines and openings into buildings.

Yes, as long as the air temperature is restricted to a range from 50° to 125° Fahrenheit and the moisture content is controlled so that the gypsum wallboard is not adversely affected. It is up to the Authority Having Jurisdiction to determine if the design meets the code requirement.

1. If the dilution required by Section 505.2 is occurring, the mixture in the duct is not flammable. Processes producing emissions that are not in work areas may have concentrations that exceed 25 percent of the LFL in the duct. These would require fire sprinklers as per Section 506.6 (2003/2006/2009/2012).

2. Calculations must be submitted that show that the required dilution to 25 percent of the LFL can be maintained within the hood in the worst-case scenarios involving the chemicals that require dilution. The AHJ may require testing to confirm that require air quantities are being exhausted based on these calculations.

Yes. The outside air provided by the HVAC system may be used as makeup air for a Type I hood.

Yes. The system would be considered a Product Conveying System and shall be terminated per Section 506.9.1, unless it is a listed system and installed per the manufacturer’s installation instructions and the listing. Additionally, the system shall comply with Sections 505.1.2 and 506.2 (2003/2006/2009/2012) and any other section in the UMC that would apply to flammable vapors. Other standards that may need to be considered are, NFPA 30 and NFPA 69 as referenced in Chapter 17 (2003/2006/2009/2012).

No. Section 506.9 applies to duct termination only. The Uniform Mechanical Code does not regulate underground gasoline storage tanks. Provisions for underground storage tanks are typically found in the Fire Code.

Yes. Garage ventilation systems in Group S, Division 3 parking garages should terminate in accordance with the provisions of Section 506.9.1, since ducts routinely convey exhaust products containing carbon monoxide, smoke, soot, water vapor, and particles of rubber from tires. Because garage ventilation systems may also be required to dissipate fumes from vehicular fuel spills, it is recommended that they should be regarded as ducts conveying flammable vapors.

No, however, it should be interpreted so as to maintain all the other required clearances outlined in this code section.

The exhaust from an enclosed parking garage is considered product conveying air since these exhausts routinely convey exhaust products containing carbon monoxide and smoke. Additionally, since garage ventilation systems may also be required to dissipate fumes from vehicular fuel spills, it is recommended that they should be regarded as ducts conveying flammable vapors.

See also UMC Answers and Analysis Section 506.9.1, Vent Termination.

The exhaust pipe for a stationary gas-powered generator is not a product conveying duct and would not be required to adhere to the requirements for termination of a product conveying duct. Additionally, to be classified as a vent, the exhaust pipe must be a listed factory-made vent pipe by definition. Most exhausts for generators are not listed and are manufactured on-site. An exhaust pipe for a generator would most resemble the definition of a chimney per the UMC, but Chapter 8 of the UMC (2003/2006/2009) only covers fuel-burning appliances and refers to NFPA 211 for appliances fueled by fuels other than gas (natural gas).

Stationary gas powered generators must be installed per the manufacturer’s installation instructions and NFPA 211, since these appliances do not fall within the scope of the UMC.

1. Yes, but only in a one-story building where the roof-ceiling assembly is not required to have a fire-resistance rating or where the hood penetrates a non fire-rated ceiling in a building more than one-story. The code states, “In buildings more than one-story in height, and in one story buildings where the roof ceiling assembly is required to have a fire resistance rating, the ducts shall be enclosed in a continuous enclosure extending from the lowest fire-rated ceiling or floor above the hood.”

2. Yes, as long as it meets the requirements of #1 and the ceiling is listed as a noncombustible.

3. Yes, as long as it meets the requirements of #1, except that if there are additional stories above the hood, an enclosure would be required commencing at the point where the grease duct penetrates the floor above.

Yes, UMC Sections 507.0 (2003/2006/2009/2012) and 508.1 requires a Type I hood above all equipment that produces comparable amounts of smoke and grease in a food-processing establishment but must not include a dwelling unit.

All commercial dishwashers require a Type II hood per Section 508.1. This is a general kitchen hood for collecting and removing steam, vapor, heat, or odors. The same amount of water vapor is released in the drying of dishes regardless of the temperature of the water used.

Section 508.1 requires hoods above all commercial-type deep fat fryers, broilers, fry grills, steam-jacketed kettles, hot-top ranges, ovens, barbecues, rotisseries, dishwashing machines and similar equipment which produce comparable amounts of steam, smoke, grease or heat in food-processing establishments. The Authority Having Jurisdiction (AHJ) would have to determine if the piece of equipment produces a comparable amount of steam to warrant the installation of a Type II hood. There are several pieces of kitchen equipment available that produce varying amounts of steam. It would be difficult to say that all steam tables require a Type II hood, when there may not be enough steam escaping to be concerned. Additionally, most kitchen and restaurants move a tremendous amount of air that may be enough to compensate for small steam producing units. The decision to require a Type II hood would have to be made by the AHJ taking into account the amount of steam being produced by the equipment and the design of the air moving system serving the space.

Aluminum is not an approved material for the construction of a commercial hood unless it meets the exception for listed hoods or it is determined by the AHJ to be equivalent in strength, fire and corrosion resistance.

The code only provides examples of low, medium and high temperature appliances. There is no specific temperature range in the code. You would have to refer to the manufacturer’s information and listing of the appliance to determine what category it might best fit.

No. The provisions for recirculating systems are now covered in Section 516.0 of the 2003/2006/2009 UMC. Several sections of Chapter 5 were revised in their entirety as a result of extractions from NFPA 96, Standard for Commercial Kitchen Equipment.

Yes. Galvanized carbon steel is allowed if it is not less than 16 gauge in thickness.

No. The 2006 UMC only allows overlapping duct connections of either telescoping or bell type for welded field joints. The examples used in UMC Figure 5-6 (2003/2006/2009) are to be used only in a duct-to-fan connection. The reason for the limitation is to prevent pocketing of grease in the duct that could result in excessive accumulation of grease.

1. Yes. Section 501.7.2 only applies to buildings more than one-story in height and in one–story buildings where the roof-ceiling assembly is required to have a fire resistance rating as addressed in Section 510.7.1.

2. No. Section 510.7.2.1 only applies to buildings defined in Section 510.7.1.

3. Section 510.7.2.3 applies to both Sections 510.7.2.1 and 510.7.2.2. All of Section 510.7.2 applies to Section 510.7.1. If you are referring to a single-story non-rated building where an enclosure is not required, all clearances shall meet the requirements as stated in Section 507.2.1.

1. No. The language in the 2006 UMC was extracted from NFPA 96, which does not require a maximum distance between a grease duct and the enclosure.

2. The Illustrated Training Manual does not necessarily misrepresent or misinterpret Section 510.7.2.3, but rather provides a recommendation to minimize the available space within an enclosure so as not to provide an invitation to install other materials in the enclosure, such as other ducts, pipes and wiring.

3. The Illustrated Training Manual is a very useful tool that can be used to compliment the provisions of the code, but should not be used for enforcement purpose.

4. No. A 5/8 inch fire-rated gypsum board is considered combustible construction. An example of limited combustible construction would be gypsum board on metal studs or solid gypsum walls and partitions as defined in the “Fire Resistance Design Manual,” published by the Gypsum Association.

1. Yes. Section 511.3, exception #1 clearly states, “when the fire extinguishing system discharges, makeup air supplied to the hood shall be shut off.”

2. Yes, same as answer #1.

3. Yes. The code does not distinguish between compensating and non-compensating hoods.

1. No. Section 517.4 addresses all solid fuel cooking systems.

2. Per Section 517.5.1 (2003/2006/2009/2012), the intent of the code is to minimize the entrance of sparks and embers into the grease control device and into the hood and duct system.

Yes, this specific appliance would require a separate hood as required in section 517.3.2 of the 2009 UMC. The manufactures instructions state that the wood is heated by the open flames creating a smoldering or slow burning process to give flavor to the meat being cooked. The wood is therefore providing a portion of the heat during the cooking process and would be required to comply with section 517.3.2.

The general requirement for hoods is listed in section 508.1 of the 2009 UMC which requires a hood for cooking appliances which produce steam, smoke, grease or heat in a food processing establishment. The UMC defines solid fuel cooking equipment as "cooking equipment that is fired with solid cooking fuel. This equipment includes ovens, tandoori charcoal pots, grills, broilers, rotisseries, barbecue pits, or any other type of
cooking equipment that derives all or part of its heat source from the burning of solid cooking fuel". Since this equipment meets the definition of solid fuel cooking equipment it shall be provided with a separate Type I hood system.

1) Yes, the total horizontal portion of the grease duct exceeds 75 feet.
2) No, it would need to be to be sloped 1 inch per lineal foot. The combined amount of horizontal duct applies.

Section 506.3 addresses fittings for all product conveying ducts, not just class 2, 3 and 4 fittings. The requirements for cleanouts apply to class 5 ducts.

Yes. The UMC does not specifically allow ventless clothes dryers. All dryer exhaust shall terminate to the outside of the building. A 4 inch dryer vent shall be installed in accordance with Section 504.0 when a compartment or space is provided for a domestic clothes dryer. Even if the AHJ does allow a ventless condensing dryer it may be possible that the owner or future owner of the property would decide to have a vented domestic dryer.

Yes, if the system is designed properly. While Chapter 5 does not cover this specific type of application, Section 103.0 does allow alternate materials and methods of construction. Mechanical exhaust ventilation shall be provided over all cooking equipment as required to effectively remove cooking odors, steam, heat grease, smoke and vapors. Mechanical ventilation is to be installed and maintained in accordance with the duct construction and exhaust requirements of the UMC. Therefore, this type of hood could meet the intent of the UMC provided the duct construction, exhaust and make-up requirements meet all other provisions of the UMC. Units that are listed and are integral to such equipment would also have to meet the allowance for installation under the listing of the equipment. With proper Technical documentation submitted to the AHJ to demonstrate equivalency, the AHJ has the authority to approve or disapprove the system.

1)    Yes, section 510.8 applies to both type I and type II to commercial food processing establishment hoods.

2)    Termination requirements for type II hood exhaust systems are found under Section 510.8 of the 2009 Uniform Mechanical Code.

3)    The UMC defines hoods in part as “An air-intake device connected to a mechanical exhaust system…” and Type II hoods as a “general kitchen hood for collecting and removing steam, vapor, heat and odors.” Section 507.0 provides the general requirements for commercial kitchen ventilation: section 510 the requirements for hoods and section 510 the requirements for exhaust duct systems.

4)    Only provisions of the UMC are under the scope of this committee.

While much of the language in Chapter 5 of the UMC was extracted from NFPA 96, the UMC was developed through technical committee and public comment, with the UMC is by itself a distinct ANSI standard and the model code for many jurisdictions. It should be noted that the annex of NFPA 96 is not part of the requirements of the NFPA document and is for informational purposes only. The language of section A3.3.33 differs from that of section 502 of the UMC.

No, this is a grease duct system therefore it must comply with section 510 of the 2006 Uniform Mechanical Code and not section 505. Section 510.6.1 requires that exterior installations “shall be vertical wherever possible”. Butt weld connections are prohibited in section 510.5.2.2; in addition any welded joint must be ground smooth on the inside and readily accessible for inspection.

Yes, while multiple solid fuel hoods can exhaust into a single solid fuel exhaust system, section 517.3.1 of the Uniform Mechanical Code states the hood for solid fuel cooking equipment shall have its own hood system, separate from any other exhaust systems. Solid fuels burn at different temperature’s and rates, the fluctuation would create vortexes and eddies that could be affected by the influx of power actuated exhaust.

1) No, section 510.8.2 of the 2012 Uniform Mechanical Code applies to both type I and II commercial hoods.
2) No, the clearance requirements for environmental air ducts would not apply for the Type II exhaust system. Examples of environmental air ducts as defined in section 207 are generally for domestic kitchen exhaust and not a Type II exhaust system.

No, the exhaust termination of an underground garage cannot be located at grade.

Ducts used for conveying car exhaust from an underground garage are classified under section 502.1 (2003/2006/2009/2012) as Class I product conveying ducts conveying non-abrasives, such as smoke, spray, mists, fog, non-corrosive fumes and gases, light fine dusts or powders. Concentrations of car exhaust in an underground parking garage will vary in concentration based on vehicle activity in the garage and cannot be considered environmental air. Parking garages have vehicles that contain flammable liquids and combustible materials; therefore if a fire occurs the exhaust system termination point and duct system would need to remove the smoke and heat from the garage.


Environmental air ducts as defined in section 207.0 do not include the exhaust from cars. A by-product of vehicle emissions is carbon monoxide. Carbon monoxide is considered a noxious and toxic gas. Since the conveyance of noxious and toxic gasses is listed under the definition of product conveying duct, exhaust from a parking garage is considered product-conveying air. The garage is ventilated to remove the contaminated air to the outside and the exhaust termination shall comply with Section 506.9 (2003/2006/2009/2012) and the product conveying ducts shall comply with Section 506.0 (2003/2006/2009/2012) with the exhaust terminating at least 10’ above the grade.

No. The terms of the listing do not overrule the minimum requirements of the Uniform Mechanical Code. Listed grease ducts do not allow you to install the grease ducts in a manner that will form dips or grease traps that will collect residues.

Yes, the condition of listing for manufactured grease ducts is applicable unless it is less restrictive than the minimum UMC requirements or violates the provisions in the UMC.

The second interpretation is correct. Where the combined amount of horizontal duct exceeds 75 feet, the duct would need to be sloped 1 inch per linear foot.

No. This is not a valid interpretation of the code. The entire length of the duct must be considered and not broken into sections. If the combined horizontal run exceeds 75 feet you would have to meet the 1 inch slope on the complete horizontal run.

Although the code does not specifically prohibit this type of installation as described, the slope of the horizontal duct would have to be 1 inch per linear foot.

No, the Uniform Mechanical Code does not consider the grease hood as a plenum. The hood for its entire length, regardless of the V-Bank grease removal filtration, is required to have protection per Sections 513.1.2 (2003/2006/2009); 513.1.1 (2012/2015), 517.3.2 (2003/2006/2009); 517.3.1 (2012/2015) and 517.7.1 (2003/2006/2009/2012/2015).

Section 513.1.2 (2003/2006/2009); 513.1.1 (2012/2015) requires that each appliance under the hood be provided with a fire extinguishing nozzle and that the fire extinguishing equipment be provided for the protection of the grease removal devices (filters). The one nozzle at the grease filters would comply with the code assuming that each cooking appliance is also protected with a fire extinguishing nozzle above.

The specific hood referred to in the question also serves as an exhaust system for a solid fuel burning charbroiler. Section 517.3.2 (2003/2006/2009); 517.3.1 (2012/2015) requires a solid fuel burning appliance shall be separated from other exhaust systems such as those exhausting grease laden vapors. The reason for this is to keep the solid fuel burning ambers from being exhausted up into the grease laden exhaust duct and causing a grease duct fire. Section 517.7.1 (2003/2006/2009/2012/2015) also covers the requirement for a fire suppression system for the hood, ducts, filters and other grease removal devices where a solid fuel burning cooking appliance is installed.

No. The prohibition on the use of butt joints only applies to field built grease ducts. Factory built grease ducts shall comply with section 510.4 Listed Grease Ducts and shall comply with the manufacturers listing requirements and joining methods as outlined in the installation instructions. The materials and connecting joints for a listed factory build grease duct have been tested for a grease duct system. If the listing or instructions provide no method for joining or welding, then Sections 510.5.2.2 (2003/2006/2009); 510.5.2.1 - 510.5.2.3 (2012); 510.5.3.2 (2015) would be applicable as field butt welds do not provide the welded joint any substantial strength when a fire occurs.

No. Sections 504.2 and 504.3 (2003/2006/2009/2012); 504.3 and 504.4 (2015) specifically requires domestic range exhaust systems and clothes dryer moisture exhaust systems be separate and distinct from each. In most cases the same types of environment air ducts could vent into a common riser. A clothes dryer moisture exhaust system would need to be installed as this is a residential high rise building and future occupants may not provide a ventless dryer. The dryer exhaust (either vented or ventless) releases lint during the process of drying the clothes into the atmosphere and the lint gathers in the duct picked up by the exhaust. If the bathroom exhaust is connected to the dryer exhaust the moisture would clog the system causing a fire hazard. Domestic range exhaust does capture and exhaust small amounts of grease laden vapors and would have an adverse effect when combined with moisture and lint. Ventless dryers are required to be provided with additional ventilation to the laundry room and the exhaust from that room shall be directly to the outside.

No, section 511.1.2 of the 2012 Uniform Mechanical Code specifically refers to in-line (exhaust) fans. Pollution Control Units are specific to their application and must be installed as prescribed in section 512.3 of the UMC and installed according to the manufacturer’s instructions.

No, non Grease Type II duct systems are not required to comply with Sec. 510.2 as they only collect and remove steam, vapor, heat, and odors. If the listing of the hood requires a clearance, then the listed clearance shall be maintained.
A Type II exhaust system does not contain, by definition, “air and grease vapors” (see Chapter 2 of the 2012 Uniform Mechanical Code). Section 510.2 is separate and distinct from section 510.1.7.

No, the 2012 Uniform Mechanical Code does not require that the make up air for commercial kitchen exhaust be conditioned. Please note 2003-2012 UMC 511.3 is "Replacement Air" 2015 UMC 511.3 is now "Makeup Air"

No, Section 501.0 of the 2015 Uniform Mechanical Code does not require any residential range to have an exhaust hood. Hood is defined in Section 210.0 in UMC to be applicable to commercial food processing equipment, it does not apply to domestic kitchens. Domestic exhaust ventilation is required in residential kitchens under Chapter 4 of the UMC as per Table 403.7. Part II of Chapter 5 expressly applies to commercial kitchens, where in addition to the exhaust hood and grease duct, a fire suppression system is required.

Yes, the termination requirements of Section 506.9 (2) apply to the wall the duct terminates on. It is not acceptable to have the product conveying duct to terminate flush to the wall. Section 506.9(2) of the 2012 Uniform Mechanical Code would apply to the termination of other product conveying ducts.

1. No, the scrubber requirement does not change this requirement that the factory-built and field built grease duct enclosures shall be protected with a through-penetration firestop system from the point at which the duct penetrates a ceiling, wall, or floor to the outlet terminal. Generally the listing requirements do not address the trough penetration.
2. Yes, the enclosure shall terminate at the outlet terminal and not at the scrubber unit.
3. Yes, a listed appliance will bear a factory applied nameplate including the agency certifying the appliance for its intended use. Only a listed appliance manufacturer’s installation instructions may allow a change or deviation from the code requirement if that system provides equivalent or superior fire resistance and safety over that which is proscribed in the UMC.

The purpose of the Uniform Mechanical Code is to “… safeguard life, health, property and public welfare.” The intent of section 510.8.2 of the 2012 Uniform Mechanical Code is to protect buildings and the public from products of heat, steam, condensation, odors and grease (even if minor).

No. While your project does not appear to comply with the requirements of the 2012 UMC, the Authority Having Jurisdiction would determine if the installation meets the intent of the Uniform Mechanical Code.

If the product being conveyed in ducts does not meet the definition of “Flammable Vapor or Fumes”, then it is not required to meet the termination distances in section 506.9 (1), and may use the distance requirements in section 506.9 (2) of the 2012 Uniform Mechanical Code.

The 2012 UMC defines “Flammable Vapor or Fumes” as constituents in air that exceeds 25 percent of its Lower Flammability Limit (LFL). If the air in a paint spray booth containing constituents never exceed 25 percent of the LFL before being exhausted would not be considered to meet the letter of the definition. If this is the case (2) would be applicable.

Comment

As for the consideration of the requirements for spray booths in the Fire Code and NFPA 33 standard, the applicable UMC product conveying duct sections are not mutually exclusive with respect to those documents.

The Uniform Mechanical Code has a narrow scope as applied to spray booths, whereas both Section 2407 of the Fire Code and Chapter 7 of NFPA 33 address both the constructability and operation of indoor and outdoor spray booth ventilation. The verbiage in section 506.9 of the 2012 UMC and section 2404.7.6 of the Fire Code is identical.

1. No. Per Section 1602.3 and Chapter 17 of the 2015 Uniform Mechanical Code, stationary engine generators are to be installed in accordance with NFPA 37 and the manufacturer’s installation instructions.

2. Yes, as long as flammable materials that are subject to spill are not being handled. The classification of the loading dock is dependent on the use and occupancy classification of the building it serves. The Authority Having Jurisdiction could allow terminations at the lessor distance if evidence is provided in a format such as a Hazardous Materials Identification Systems (HMIS) summary.

The termination requirements are the same. Section 502.2.2 of the 2015 Uniform Mechanical Code is specific in its requirements and does not distinguish between horizontal or vertical installations for other product-conveying outlets. It simply states that they shall (prescriptive) terminate not less than 10 feet from a property line, 3 feet from exterior walls or roofs, 10 feet from openings into the building, and 10 feet above adjoining grade.

Yes it would be considered an opening to the building when determining exhaust termination distances.

No. This section pertains to Type I Exhaust Systems

For wall-mounted canopies, only the front or total length of the hood is used for the calculation.

For example Table 508.10.1.2 requires 550 CFM per linier foot for a wall mounted canopy and if the front of the hood measured 10 feet the required total CFM would be 5,500 CFM

1. Yes, all seams, joints, and penetrations of a hood enclosure where grease vapors could accumulate shall be sealed. Although the joint between the two hoods is not within the enclosure, the joint provides a place where grease vapors could accumulate and must be sealed. Section 508.7 of the 2015 Uniform Mechanical Code states that Seams, joints, and penetrations of the hood enclosure that direct and capture grease-laden vapors and exhaust gases shall have a liquid-tight continuous external weld to the hood’s lower outermost perimeter.

2. No specific material is recommended but any material/product used must meet the definition of liquid-tight in Chapter 2 of the UMC as “… not to permit the passage of liquid at any temperature.” Guidance can also be found within Annex A of NFPA 96 which defines a continuous weld as: Welding is a fabrication technique for joining metals by heating the materials to the point that they melt and flow to form an uninterrupted surface of no less strength than the original materials.

Yes, a listed Type 2 dryer equipped with a lint filtering system would meet the minimum standards of Section 504.4.3.1 (3) of the 2015 Uniform Mechanical Code.

The manufacturers listing of the equipment might require other means for lint control such as an exhaust fan interlocked with dryer operation and include cleanouts within the exhaust piping.

1. No, the 2012 Uniform Mechanical Code does not require that a kitchen exhaust be installed for either a residential gas or electric range. The UMC only provides installation requirements for when a hood is installed. The proscriptive requirements cited in Chapter 4 of the UMC addresses kitchen ventilation as a space, not specifically to the exhaust at a listed ranges or built-in domestic cooking units.

2. No, the UMC does not address fuel differences.

3. The UMC does not address this since it is not required

No the 2012 Uniform Mechanical Code does not contain provision for tempering the makeup air for a kitchen exhaust hood.

The Authority Having Jurisdiction may adopt Appendix E of the 2012 UMC or other energy standard that requires the control of enthalpy/tempering for make up air.

1. Section 504.1 specifically states that any duct provisions that are not addressed in Chapter 5 will be addressed in Chapter 6. The second exception for this section recognizes that ductless and condensing (ductless) clothes dryers do not require an exhaust duct where installed in accordance with the manufacturer’s installation instructions. The use of this exception would only be applicable if this type of appliance was to be permanently installed for the useful life of the building. During final inspection building, the dryer is not typically installed, thus the inspector does not know what type of dryer an owner will be providing. The only way to ensure that all types of dryers are accommodated for is to install an exhaust duct per Section 504.4.2 in all laundry rooms.
2. This exception started with the 2015 code cycle.

1. No. They must be independent. These two processes are considered by code two different environmental exhaust systems.
2. No, as long as the HRV is installed per the listing and the manufacturer’s installation instructions as specified in UMC Section 504.5. This system would be acceptable if the exhaust grills are far enough apart.
3. Yes. Kitchen range exhaust shall be separate from bathroom exhaust and shall operate independently of each other.

Flexible connectors are not allowed in a grease duct in line exhaust fans inside the building. Additionally NFPA 96 sections 8.1.2.3 and 8.1.3.4 specifically prohibit the use of flexible connectors in grease duct systems. Sections 510.9.1.1 and 511.1.3.1 were previously added to the Uniform Mechanical Code in 2003 by the NFPA 96 task group.

1. Yes, hot wells and heat tables that produce steam, heat, vapors or odors unless they are otherwise listed. It is determined by the Authority Having Jurisdiction rather the equipment generates steam or heat.

2. No, the code does not define a minimum of output of vapor, steam, odor, and the temperature at which they are generated. Section 508.1 Exceptions 1 through 4 of the 2015 Uniform Mechanical Code specify the conditions when the equipment does not require a hood.

1. No, while section 504.2 prohibits combining the exhaust systems, it is not the intent of section 504.2 to use the air classes found in table 402.1 to determine whether the air has to be exhausted independently. Section 504.2 pertains to environmental air only. The intent of 504.2 is to prohibit an environmental air duct system from being combined with other environmental air duct systems serving a different purpose. Independent ducts minimize the potential spread of contaminants, hazardous exhaust, fire, or smoke to other parts of a building. Environmental air is defined as air not exceeding temperatures of 250 degrees Fahrenheit to or from occupied areas of any occupancy through other than heating and air-conditioning systems, such as ventilation for human usage, domestic kitchen range exhaust, bathroom exhaust ducts, and domestic-type clothes dryer exhaust ducts.

2. No, not specifically. They are described as “environmental air ducts, product-conveying systems, and commercial hoods and kitchen ventilation” in in Chapter 5 section 501.1 Applicability. Where there is an absence of the specific term “Exhaust System” within the definitions of the 2015 Uniform Mechanical Code each individual term does have a definition in Chapter 2 of the UMC.

3. Yes

4. No, air class is used to identify the quality of the air based on its content and odor.
5. No, Table 402.1 MINIMUM VENTILATION RATES IN BREATHING ZONES, is applicable to outdoor air rates for occupants of a building or occupancy, the exhaust airflow shall be provided in accordance with the requirements in Table 403.7.

Yes it is allowed to terminate an environmental exhaust duct eight feet above grade, but not above a public walkway. The intent of the code is to prevent exhaust air from exhausting directly on the walkway users so they are not subjected to the fumes or other by-products. The 2015 Uniform Mechanical Code states that the environmental duct shall not discharge onto a public walkway. The last sentence of section 502.2.1 clearly states no discharge onto a public walkway. Environmental ducts have situations that could cause action upward and downward. No allowable distance is given for discharge onto a public way.

No, Exemption (1) would not pertain to a Type II hood. Section 508.1, Exception 1 of the 2015 Uniform Mechanical Code references UL 710B and only pertains to a Type I hood. UL 710B is a standard for Recirculating Hood Systems (ductless hoods). A recirculating hood is described by UL as “A recirculating hood system includes a fan, a collection hood and an air filtering system consisting of a grease filter, and may incorporate other air filtering devices”. Additionally Exemption I specifically states it is for appliances with reduced emissions for ‘grease discharge, which is applicable to a Type I hood. A type II hood cannot be installed above equipment where smoke or grease is present.

Further clarification can be found in Chapter 13 of NFPA 96-2017.

No, the Term/Phrase “Other exhaust systems” would not refer to Product Conveying Exhaust systems. Any system that falls outside the listed category of “Environmental Air Duct” in section 504.0 would be covered elsewhere in Chapter 5 of the 2015 Uniform Mechanical Code. Section 505.0 of the 2015 Uniform Mechanical Code is specifically applicable Product Conveying Exhaust Systems; Section 506.0 is specifically applicable Product Conveying Exhaust Ducts; and the balance of the Chapter is devoted to Commercial Kitchens Ventilation

No, Section 510.1.3 of the 2015 Uniform Mechanical Code does not pertain to Type 2 ducts. Section 510.1.7 of the 2015 UMC pertains to Type 2 duct systems. Type 2 exhaust duct used with a moisture related process such as a dishwasher would be required to drain back to the hood.

The verbiage in section 510.1.3 of the 2015 Uniform Mechanical Code is an extraction from NFPA 96. The specific slope requirement in section 510.1.3 would only apply to grease ducts serving Type I hoods.

Yes, a spark arrester is required when using solid fuels. The first sentence in Section 517.1.6 of the 2015 Uniform Mechanical Code states that any solid fuel cooking operation requires spark arrestors to protect embers from entering a duct or plenum. The second sentence specifically addresses equipment not located under a hood, and also requires a spark arrestor to minimize embers from passing through a flu or chimney. These two sentences do not contradict one another but compound the requirement for spark arrestors for solid fuel cooking applications whether they are integral to the equipment or not. Please also refer to NFPA 96-14.1.1 and 14.1.7.

No, Section 504.3 of the 2015 Uniform Mechanical Code is referring to the pipe alone as being smooth. You are still required to have the 3 metal screws. The intent of the code is to maintain a smooth interior surface to allow proper and unobstructed airflow of the exhaust to its termination and to allow grease to drain back towards the hood. Attaching a vent to the hood exhaust outlet may or may not violate the manufacturer’s installation instructions, however it does not specifically violate the code.

No, there is no height limitation as long it is not less than 6 inches beyond the edge of the cooking surface on the open sides, and the vertical distance between the lip of the hood and the cooking surface does not exceed 4 feet from the highest cooking surface.

For a multi-deck pizza oven with more than one cooking surface the lowest cooking surface would be determined by the cooking surface furthest vertically (i.e. the highest) from the lip of the hood providing it does not exceed the maximum allowable distance of 4 feet.

Yes, a Type I Hood is required for exhausting a solid fuel pizza oven. Solid fuel cooking is defined in the 2015 Uniform Mechanical Code as Extra-Heavy-Duty Cooking Appliances under section 508.10.1.2.

1. No, the 2015 Uniform Mechanical Code does not specify that the hood & backdraft be listed. Chapter 17 of the 2015 UMC, Referenced Standards do not list parts of a single residential dryer vent system, except that electric dryers are installed in accordance with the manufacturer’s installation instructions. Clothes Dryer duct is an environmental air duct and does not need to be listed or third party approved for dryer exhaust. The 2015 UMC requires the duct to be constructed of rigid metallic material and shall have smooth interior surface and not be less than 4 inches nominal and the thickness shall not be less than 0.016 of an inch. The duct shall be installed in accordance with Chapter 6.

#2. No, Backdraft dampers for clothes dryers are not required to be listed or third party approved.

No, Fire dampers are generally not installed on exhaust ducts and may be prohibited as stated in section 505.6.1 of the 2018 Uniform Mechanical Code. Section 506.3.1 of the 2018 UMC is specific to a product-conveying ducts that passes through a fire barrier having a fire resistance rating of 2 hours or more. The code then states you shall meet one of the three specifications listed.

The intent of these sections, in conjunction with section 608.1(4) of the 2018 UMC and Chapter 7 of the building code, is to provide assurance that the vapors, mists and gases that might be created would be exhausted to the exterior of the building providing fire and life safety to the occupants of the building and emergency personal that would be responding to any incidents.

Yes, the 2015 Uniform Mechanical Code is specific on that a flow switch or transducer shall be provided. If not part of the listed equipment a field installed flow switch or transducer listed under UL 710 or UL 1978 listing would meet this code sections intent. Neither 518.4 nor NFPA 96 mention what type of flow switch is required, just that one is needed. If the flow switch meets the other two UL ratings that would or should be acceptable. The field supplied flow switch would need to be installed as per 510.5.3 Exception (3) penetrations shall be permitted to be sealed by other listed devices that are tested to be grease tight and are evaluated under the dame conditions of fire severity as the hood or enclosure of listed grease extractors and whose presence does not detract from the hood or the ducts structural integrity.

1. No, this would not meet the intent of the code. Runs exceeding 75ft. would need to meet the 8% minimum slope requirement for their entire length. Ducts shall be installed with not less than 2 percent slope on horizontal runs up to 75 feet and not less than 8 percent on horizontal runs more than 75 feet.
2. This is not applicable as the code is specific to slope under this specific application.
3. No, neither would be applicable. Option 2 forms dips or traps. Option 3 pitches away from the hood.

1. Yes, based on your description this would be one space and the process is bathroom exhaust.
2. No, there is no need to separate systems for this process as long as the exhaust system is adequately sized and all other code intent is met. In Table 403.7 locker rooms and public toilet rooms have different rates of exhaust. Locker room exhaust rate is 0.50 (cfm/sq.ft.) or locker room/dressing room the exhaust rate would be 0.25 (cfm/sq.ft). water closets are rated at 50/70 cfm per water closet, urinal, or both. The higher rate is for periods of heavy use otherwise the lower rate is permitted to be used. There is also a foot note 9 that states that toilet exhaust air that has been cleaned in accordance with the criteria of Class 1 shall be permitted to be recirculated.
3. No, they are the same Class 2 Air. These would both be classified as the same environmental exhaust, however the minimum exhaust rates of Table 403.7 must be maintained.

Yes, section 504.2 of the 2015 Uniform Mechanical Code would still apply. Specific to section 504.2 the applicability is determined specifically by the type of exhaust and that it be independent to other exhaust systems. There are no exceptions listed in this section to this requirement. You must have independent environmental air exhaust systems to prevent cross contamination of exhausted grease, moisture and lint in the duct system.

No, it is not acceptable under the provisions of the 2018 Uniform Mechanical Code for a factory-built product to be listed exclusively by ASTM E2336. Section 507.4.4 of the 2018 Uniform Mechanical Code states that the factory-built grease duct protection system be UL 2221 and the enclosure through penetration system would need to meet ASTM E814 or UL 1479.

These code sections were originally brought into the Uniform Mechanical Code in the August 2007 Report On Proposals. As noted in the substantiation submitted by Theodore C. Lemoff of NFPA::

This proposal seeks to further clarify the application of UL 2221 and ASTM E2336 related to the test methods for testing grease duct enclosure protection materials and systems. This proposal makes the application of the UL 2221, Standard for Tests of Fire Resistive Grease Duct Enclosure Assemblies, and ASTM E 2336 Standard Test Methods for Fire Resistive Grease Duct Enclosure Systems consistent with recent changes adopted in the International Mechanical Code. As indicated by the proposal, these changes make UL 2221 applicable to factory-built grease duct enclosures, and ASTM E2336 applicable to field-applied grease duct enclosure systems. This proposal is also consistent with the manner in which these two Standards are employed by the affected industries. In addition, the requirement to fire stop around the exterior of the grease duct enclosure is also added for consistency with the model Codes.

Code change proposals to the Uniform Mechanical Code are beyond the scope of work of the UMC Answer and Analysis committee. IAPMO utilizes an open consensus process accredited by the American National Standards Institute (ANSI) in its code development practice. Members and non-members alike—can submit proposed changes to the code. More information is available at
http://www.iapmo.org/codes-standards-development/

Yes. Ducts handling materials at temperatures in excess of 900 degrees shall be lined internally as per section 506.10.4.1 and the duct shall also have 24 inch clearance to unprotected surfaces as per table 506.10.4 The 2018 Uniform Mechanical Code does not define the terms “Duct Liner” or “Duct Wrap”. Historically it is understood in the industry that “Duct Liner” is installed internally in the duct while applications on the outside would be lagging. See also SMACNA Accepted Industry Practices for Sheet Metal Lagging, 1st Edition

UL 1995 is not acceptable as a more stringent substitute for UL 1812. Section 504.5 of the 2018 Uniform Mechanical Code only states UL 1812. UL Standard 1812 is specifically applicable to ducted heat recovery ventilators, whereas UL Standard 1995 has a much broader application as it references HVAC in general. The criteria of UL 1812 includes construction and performance standards for equipment listed for outdoor-use where UL 1995 does not.

1. Yes. This exhaust air could be considered as class 5 due to the potential for acid vapor as the lead-acid is corrosive. Hydrogen is flammable, when the hydrogen concentration rises to levels above 4% there is a substantial risk of an explosion.
2. The first paragraph one is applicable to this installation.
3. Section 502.2.2 of the 2018 Uniform Mechanical Code is not the only regulation the termination would need to comply with. Consideration would also need to be given to NFPA 70 section 706.10, with additional reference to the Fire Code and IEEE 1635-2012/ASHRAE 21-2012.

Condensing Dryers are not under the scope of §504.4 of the 2018 Uniform Mechanical Code. They are covered under the provisions of §504.1 exception 2. “Condensing clothes dryers where installed in accordance with the manufacturer’s installation instructions.”

1. No. Section 519.5 (2) of the 2018 Uniform Mechanical Code states that a Type II Hood Exhaust horizontal termination shall not terminate be less than ten feet from operable openings to buildings. Section 519.5 (1) of the 2018 UMC also states that if a Type II Hood Exhaust outlet is a horizontal termination the exhaust termination shall be at least 40" above the roof's surface, a minimum distance of 10 feet from the property line with the exhaust flow shall be directed away from the roof surface. Additionally kitchen exhaust air is listed as Class 2 Air, which is ‘…inappropriate for transfer or recirculation to spaces used for different purposes.’

2. No. Section 502.2.1 of the 2018 UMC states that environmental air ducts shall terminate not less than three feet from openings into the building.

3. Yes, this is correct. While the UMC does not specifically provide a definition for a roof opening hatch, OSHA does provide a definition of opening -a gap or open space in a wall, partition, vertical walking /working surface or similar surface in which an employee can fall to a lower level. Therefore, a roof hatch would be considered to be an operable opening as per section 519.5(2) of the 2018 UMC.

1. No. The 2015 Uniform Mechanical Code does not address that a Type II downdraft exhaust system for a non grease and a non smoke appliance cannot be used. Section 518.0 does not prohibit Type II downdraft exhaust systems which would serve appliances that produce little or no grease. If the downdraft ventilation system is classified as Type II, provisions of Section 510.1.7 would be applicable to the ductwork.

2. Yes, if the Authority Having Jurisdiction, under provisions of Section 508.1 of the 2015 UMC, makes the determination that the hot pot appliances are of Type II and not Type I because grease or smoke is not present, or if the cooking appliance meets UL 710B [Section 508.1(1) requirements] then the ductwork requirements for a Type II exhaust system can be used. The AHJ would take into account the type of food being cooked and specify the amount of grease produced. If the cooking process uses oil or animal protein, grease laden vapors will be produced. The amount of these vapors will determine if a Type I duct is required. If the downdraft ventilation system is classified as Type I, provisions of Section 510.1.3 would be applicable.

Section 506.8 of the UMC proscribes that if the greatest diagonal dimension of the duct, regardless of duct shape of the duct, exceeds 10 inches then sprinklers shall be installed. Historically, product-conveying ducts carrying flammable fumes or vapors such as the exhaust for a fume hood are generally round ducts (spiral). This would imply that the intent of this section is to address a round exhaust duct. In the code it does not state anything about cross sectional area. Though possible and not prohibited by code it would be rare for a design to call for square duct in a product conveying system where the duct would be carrying flammable fumes or vapors. Cross sectional dimension of a round duct is always the same yet on a square duct, rectangular duct, even an oval duct have different cross sectional dimensions and if any of them exceed 10 inches then sprinklers shall be installed. The dimension of the duct diameter takes precedent regardless of the shape of the duct. To determine the diameter for a round duct use the formula D = 2 × r; to determine the diameter for a square duct use the formula a√2 where a = side; To determine the diameter for a rectangular duct use the formula d² = a² + b² where a is the width of the rectangle and b is the height of the rectangle. In those rare instances where the duct is oval in shape, you would use the major axis as the length of the diameter.

1. Section 502.2.1 of the 2018 Uniform Mechanical Code, prohibits environmental exhaust ducts discharge onto a public walkway.
2. No, as this would not meet the requirement of not discharging onto a public walkway.

1. Yes, they are separate applicable requirements of the 2018 Uniform Mechanical Code. UMC section 403.7 and table 403.7 establish the proscribed exhaust rates so that the proper amount of make up air can be provided to the said space, whereas UMC section 504.1 is a general requirement that states what material is required and how it is to be installed. Section 504.1 does not give direction on the amount of air that needs to be exhausted by the duct. Additionally, Chapter 6 provides ducts shall be airtight.

2. No that is not correct. Section 504.1 (1) exception applies to the construction of the duct. This would exempt a ductless range hood construction, since there is no duct in this application. UMC section 405.4 states in part: ‘A mechanical exhaust directly to the outdoors shall be provided in each kitchen…’ UMC section 403.7 does state that exhaust make up air shall be permitted to be combination of outdoor air, recirculated air, and transfer air. Even though a ductless range hood is a recirculating exhaust it is still considered exhaust, but it does not satisfy the requirements of UMC section 405.4. Jurisdictions also have different indoor air quality requirements based on the building occupancy and adopted energy code.

No. Any fastener that penetrates the the dryer duct that can catch lint is not allowed. Rivets would extend into the duct and that are capable of catching lint and reduce the efficiency of the exhaust system.

Yes, section 504.4.3.1 of the 2021 Uniform Mechanical Code states that where ducts pass through walls, floors, or partitions, the space around the duct shall be sealed with a noncombustible material and section 504.4.4 states the common exhaust duct shall be of rigid metal and be installed in a fire-resistant rated enclosure In accordance with the building code. The duct material shall be of rigid metal with a thickness of 0.020 of an inch (24 gauge). The duct enclosure shall be provided with a cleanout opening of not less than 12 inches x 12 inches. Duct wrap is not required and a six inch clearance from adjacent combustible material is only required if The Type II Dryer is unlisted. Ducts that pass through firewalls or fire separations are required to have smoke/fire dampers and cannot pass through corridors, but these ducts do not include dryer exhaust. Committee Response to Comment:
The type of system described in the comment meets the requirements of Section 504.4.4 of the 2021 UMC. Please note that Section 604.1 refers to Furnace Plenums and Air Duct, not exhaust duct for clothes dryers. Any fire protection requirements would be in the Building or Fire Codes. If a fire or fire/smoke damper is required by these codes, any alternative means/methods to their requirements must also be found in the respective codes. The Authority Having Jurisdiction can interpret the building, fire, and mechanical codes, resolve conflicts between codes, and allow alternative materials and methods that are equivalent in safety and fire resistance.

The exhaust duct from the paint workshop would be classified as product conveying duct with the provisions for duct clearances specified under the 2015 Uniform Mechanical Code §506.7. Your proposed design would need to be considered by the Authority Having Jurisdiction as an Alternative Means and Method to provide reduced clearances to limited combustible material, while still meeting the provisions of UMC §506 and Chapter 7 of the Building Code. The type X sheetrock is limited combustible material. If the product exhaust duct is treated as a grease duct, then a (3) inch clearance is all that is required through the enclosure beyond the ASTM E2336 fire rated duct wrap. The shaft described in the question would need to be constructed as defined in §214.0. he manufacturers listing of the fire wrap would be the basis for the termination at the shaft where the wrap and enclosure meet.

No, an optical or acoustical device/indicator is not considered equal to the function of an interlocking device.

(2018/2021) UMC Section 519.1 (2), (2015) UMC Section 508.1 (4) states that an interlocking device is required in the installation of this equipment. Optical and acoustical indicators are for operator information and only signal to operators not to open the appliance early. Optical or acoustical device/indicators do not satisfy (2018/2021) UMC Section 519.1 (2), (2015) UMC Section 508.1 (4) because they do not function as “an interlocking device to prevent opening of the appliance”.

1. Yes. Existing Type I and Type II hoods and exhaust systems shall be considered non-listed and shall be inspected by The AHJ in accordance with sections 508.3 and 508.5 (2015/2018/2021) Uniform Mechanical Code.
2. Yes. It would need to meet the currently adopted UMC requirements of a non-listed hood.

1. No a ductless dryer, which is the same as a condensing dryer, shall be installed in conformance with manufacturer’s listing and installation instructions per the (2015/2018/2021) Uniform Mechanical Code section 504.1 exception (2).

Condensing clothes dryers where installed in accordance with the manufacturer's installation instructions do not require an exhaust duct in accordance with the (2015/2018/2021) UMC section 504.4.2.

2. Exception (2) of section 504.1 applies to section 504.0 its entirety.

Yes, per (2015/2018/2021) UMC section 508.4 and section 510.3.3.3, duct supports, or support systems are code required by design to be capable of supporting horizontal grease duct system loads twenty-four inches and larger plus 800 lbs. Additionally at any point in the duct systems as the stresses exerted on the corners, edges and welded seams of the ducting can cause premature failure.

The seismic restraint design of the support system would need to comply with ASCE 7-16 13.6 or SMACNA Seismic Restraint Manual.

The UMC does not make specific references to elements of the building structure such as trusses or roof members as this would be determined by the building code taken into consideration by the designers.

No, as long as equipment meets the requirements of section 508.1 and 516.0 of the 2021 Uniform Mechanical Code, the recirculating system would be approved under the exception. A recirculating system does not exhaust to the outside, where a type II exhaust does. A bakery oven could produce smoke and grease, therefore equipment in compliance with UL710B along with the requirements on 516.0 would meet the intent of the UMC.

1. No, unless all of the intent of this section is met which also requires the termination to be not less than 30 feet from a property line, 10 feet from openings into the building, and 6 feet from exterior walls or roofs. Your illustration does not provide the necessary detail or distances to determine this.

1. No, bathroom exhaust and a janitors closet exhaust must be kept independent of one another and separated as these are considered to be incompatible exhausts. This section of the code does allow like or compatible exhausts to be combined provided they do not violate any other section of the code. Exhaust systems that may be combined would depend on the particular building situation. With the risk of a janitor’s closet containing chemicals, which could be spread into the adjoining bathrooms via the exhaust, it would require Authority Having Jurisdiction (AHJ) approval to combine those exhaust systems.

2. The only circumstances where exhaust maybe combined by the code into a common duct is when they are compatible. Typically, the same type of exhaust may be combined with a common exhaust fan interlocked to run when any exhaust is used. For example, multiple bathrooms may be combined to exhaust into one duct as long as the design included backdraft protection per 504.1.1 2021 Uniform Mechanical Code. This may or may not be prohibited by local codes or ordinances and are subject to approval by the local AHJ.

There is no maximum length indicated because section 504.4.2.2 of the 2018 Uniform Mechanical Code is for Type I dryers (domestic use in a residential occupancy). The UMC does not specify length for commercial dryers.

Ducts used for conveying car exhaust from an garage are regulated under section 502.2.2 of the 2021 Uniform Mechanical Code: “Other product-conveying outlets shall terminate not less than 10 feet (3048 mm) from a property line, 3 feet (914 mm)from exterior walls or roofs, 10 feet (3048 mm) from openings into the building, and 10 feet (3048 mm) above adjoining grade.” These are Class I product conveying ducts conveying non-abrasives, such as smoke, spray, mists, fog, non-corrosive fumes and gases, light fine dusts or powders. Concentrations of car exhaust in an underground parking garage will vary in concentration based on vehicle activity in the garage and cannot be considered environmental air. Parking garages have vehicles that contain flammable liquids and combustible materials; therefore if a fire occurs the exhaust system termination point and duct system would need to remove the smoke and heat from the garage.

A by-product of vehicle emissions is carbon monoxide. Carbon monoxide is considered a noxious and toxic gas. Since the conveyance of noxious and toxic gasses is listed under the definition of product conveying duct, exhaust from a parking garage is considered product-conveying air.

Vehicle exhaust by definition is not flammable as it has already combusted in the engine.

However, if there are facilities within the garage for the transfer of flammable fuel to vehicles, then that exhaust from the area of the garage would need to meet the clearance requirements of “explosive or flammable.”

The Authority Having Jurisdiction interprets the Mechanical Code. The AHJ could allow terminations at the lessor distance if evidence is provided in a in an Alternative Means and Methods format such as a Hazardous Materials Identification Systems (HMIS) summary as flammable materials that are subject to spill are not being handled.

An enclosed parking garage exhaust system is classified as a product conveying system.

Given the information provided in your comment this would not meet the intent of the 2021 Uniform Mechanical Code. Under the specific parameters where the range exhaust and dryer exhaust are independent and separate, the general exhaust in a residential condominium building from a restroom and kitchen can be combined, but not the laundry room.

The 2021 Uniform Mechanical Code does not specifically prohibit general exhaust from different room types being combined. The 2021 UMC does have regulations for ventilation and exhaust air. Refer to the definitions in Chapter 2 for the different classes of air for return, transfer, or exhaust air.

It is the intent of the UMC that the kitchen range hood, dryer exhaust and bathroom exhaust be independent. The additional information at the link states that the kitchen range and dryer exhaust are separate, which complies with the intent of the 2021 UMC. However, Section 504.2 and the exhaust of the different Air Classes clearly does not allow combining such systems. Bathroom and kitchens are the same air type (class 2). Laundry is a (class 1.) It should also be noted that within Tables 5.1 and 5.2 of ASHRAE 62.2 (see 1701.2 of the 2021 UMC) kitchens and bathrooms are listed within the same grouping. Air from laundry areas is not included.

If the proposed exhaust air is intended to be recirculated as environmental air, then section 403.9 of the 2021 UMC would also be applicable. See section 311.3 of the 2021 UMC for prohibitions on sources of return air. Additionally, energy recovery ventilators (ERVs) are covered by AHRI 1060, which allows a percentage of exhaust to be recirculated. ERVs listed to AHRI 1060 may not be supplied with restroom exhaust unless that restroom exhaust is first filtered to Class 1 air per 2021 UMC Table 403.7, Note 9: “Exhaust air that has been cleaned in accordance with the criteria of Class 1 shall be permitted to be recirculated.”

No, moisture removal and heat removal for condensing clothes dryers, also known as ventless clothes dryers are not specifically addressed in the 2021 Uniform Mechanical Code for either low rise residential or multifamily residential occupancies.

Historically condensing appliances not specifically addressed in the UMC would be governed by the manufacturer’s listening and installation requirements as set forth by an approved third party ANSI accredited listing agent. Minimum code requirement may be more restrictive as Chapter 12 of the Building Code requires contaminants in naturally ventilated be exhausted in accordance with the Mechanical Code; if the Authority Having Jurisdiction the level of moisture would be considered Class 2 Air (see Chapter 2 of the UMC) then the ambient moisture would be exhausted in compliance with the Energy, Green Building Standard or Appendix E of the UMC.
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There are no recognized and generally accepted good engineering practices around moisture removal and heat removal from the living space, nor are there any specific requirements in section 504 of the 2021 Uniform Mechanical Code.

The EPA does publish guideline EPA 402-F-13053 that suggest less than 50% relative humidity at 75°F for high indoor air quality (IAQ) and to prevent mold growth. IAQ will vary with occupancy, season and geography so a prescriptive requirement in the code cannot address this complex issue.