Page 77 - 2018_IMC

EXHAUST SYSTEMS

508.1.1 Makeup air temperature. The temperature dif- flammability limit of the substance for the expected
ferential between makeup air and the air in the conditioned room temperature.
space shall not exceed 10ºF (6ºC) except where the added 2. A vapor, gas, fume, mist or dust with a health-hazard
heating and cooling loads of the makeup air do not exceed rating of 4 is present in any concentration.
the capacity of the HVAC system.
3. A vapor, gas, fume, mist or dust with a health-hazard
508.1.2 Air balance. Design plans for a facility with a rating of 1, 2 or 3 is present in concentrations exceed-
commercial kitchen ventilation system shall include a ing 1 percent of the median lethal concentration of the
schedule or diagram indicating the design outdoor air bal- substance for acute inhalation toxicity.
ance. The design outdoor air balance shall indicate all
exhaust and replacement air for the facility, plus the net Exception: Laboratories, as defined in Section 510.1,
exfiltration if applicable. The total replacement air airflow except where the concentrations listed in Item 1 are
rate shall equal the total exhaust airflow rate plus the net exceeded or a vapor, gas, fume, mist or dust with a health-
exfiltration. hazard rating of 1, 2, 3 or 4 is present in concentrations
exceeding 1 percent of the median lethal concentration of
508.2 Compensating hoods. Manufacturers of compensating the substance for acute inhalation toxicity.
hoods shall provide a label indicating the minimum exhaust [F] 510.2.1 Lumber yards and woodworking facilities.
flow, the maximum makeup airflow or both that provides
capture and containment of the exhaust effluent. Equipment or machinery located inside buildings at lum-
ber yards and woodworking facilities that generates or
Exception: Compensating hoods with makeup air sup- emits combustible dust shall be provided with an approved
plied only from the front face discharge and side face dis- dust-collection and exhaust system installed in accordance
charge openings shall not be required to be labeled with with this section and the International Fire Code. Equip-
the maximum makeup airflow. ment and systems that are used to collect, process or con-
vey combustible dusts shall be provided with an approved
explosion-control system.
SECTION 509
FIRE SUPPRESSION SYSTEMS [F] 510.2.2 Combustible fibers. Equipment or machinery
within a building that generates or emits combustible
509.1 Where required. Cooking appliances required by Sec- fibers shall be provided with an approved dust-collecting
tion 507.2 to have a Type I hood shall be provided with an and exhaust system. Such systems shall comply with this
approved automatic fire suppression system complying with code and the International Fire Code.
the International Building Code and the International Fire
Code. 510.3 Design and operation. The design and operation of the
exhaust system shall be such that flammable contaminants
are diluted in noncontaminated air to maintain concentrations
SECTION 510 in the exhaust flow below 25 percent of the contaminant’s
HAZARDOUS EXHAUST SYSTEMS lower flammability limit.
510.4 Independent system. Hazardous exhaust systems shall
510.1 General. This section shall govern the design and con-
struction of duct systems for hazardous exhaust and shall be independent of other types of exhaust systems.
determine where such systems are required. Hazardous 510.5 Incompatible materials and common shafts. Incom-
exhaust systems are systems designed to capture and control patible materials, as defined in the International Fire Code,
hazardous emissions generated from product handling or pro- shall not be exhausted through the same hazardous exhaust
cesses, and convey those emissions to the outdoors. Hazard- system. Hazardous exhaust systems shall not share common
ous emissions include flammable vapors, gases, fumes, mists shafts with other duct systems, except where such systems are
or dusts, and volatile or airborne materials posing a health hazardous exhaust systems originating in the same fire area.
hazard, such as toxic or corrosive materials. For the purposes Exception: The provisions of this section shall not apply
of this section, the health-hazard rating of materials shall be to laboratory exhaust systems where all of the following
as specified in NFPA 704. conditions apply:
For the purposes of the provisions of Section 510, a labo- 1. All of the hazardous exhaust ductwork and other
ratory shall be defined as a facility where the use of chemi- laboratory exhaust within both the occupied space
cals is related to testing, analysis, teaching, research or and the shafts are under negative pressure while in
developmental activities. Chemicals are used or synthesized operation.
on a nonproduction basis, rather than in a manufacturing pro- 2. The hazardous exhaust ductwork manifolded
cess. together within the occupied space must originate
510.2 Where required. A hazardous exhaust system shall be within the same fire area.
required wherever operations involving the handling or pro- 3. Hazardous exhaust ductwork originating in different
cessing of hazardous materials, in the absence of such fire areas and manifolded together in a common
exhaust systems and under normal operating conditions, have shaft shall meet the provisions of Section 717.5.3,
the potential to create one of the following conditions: Exception 1, Item 1.1 of the International Building
1. A flammable vapor, gas, fume, mist or dust is present Code.
in concentrations exceeding 25 percent of the lower 4. Each control branch has a flow regulating device.

60 2018 INTERNATIONAL MECHANICAL CODE 
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