(2) An employer shall provide a mechanical air supply system if its absence will
result in building negative pressures sufficient to cause back-drafting of vents from fuel-
fired equipment or ineffective control.
(3) Mechanical air supply volumes shall be heated to maintain a minimum air
temperature of 65 degrees Fahrenheit measured at the point of air discharge to the space.
Exceptions to this requirement are refrigerated storage rooms, special process rooms, and
similar locations where low air temperatures are essential to the preservation of the
product or service, or, if in the opinion of the director, a lower air temperature will not be
harmful to the health of the persons affected.
(4) Make-up air for spray-finishing operations shall be as prescribed in General
Industry Safety Standard Part 76 “Spray Finishing Using Flammable and Combustible
Materials,” as referenced in R 325.52002.
(5) Make-up air for open surface tanks shall be as prescribed in Occupational Health
Standard Part 526 “Dipping and Coating Operations,” as referenced in R 325.52002.
History: 2005 AACS; 2016 AACS.
R 325.52006 Direct-fired air heaters.
Rule 6. (1) A direct-fired air heater, wherein combustion products are released
in the supply air stream, may be installed in buildings of industrial occupancy,
garages, laundries, and commercial kitchens. They shall not be installed in offices,
schools, hospitals, and places of public assembly.
(2) A direct-fired air heater shall have an inlet duct connected directly to the out-of-
doors. Room air shall not be circulated across the burner.
(3) A direct-fired air heater shall deliver air which contains not more than 10 ppm
of carbon monoxide and is free from odors of combustion products. Permissible
concentrations of other contaminants in the delivered air may be established by the
director pursuant to their permissible exposure limits and the degree of exposure to a
(4) The air volume supplied to the building by a direct-fired air heater shall
not exceed 110% of the total air volume exhausted. The director may require
interlocking of a heater control system with an
exhaust ventilation system if necessary to ensure that the exhaust systems are
(5) A direct-fired air heater shall have both of the following:
(a) A pre-ignition purge of fresh air.
(b) A positive fuel supply closure in the event of fuel supply failure, ignition
failure, flame failure, power failure or interruption, or air flow reduction below 50% of
its rated capacity.
History: 2005 AACS.
R 325.52007 Exhaust ventilation systems.
Rule 7. The minimum rate of exhaust ventilation for places of
manufacturing, processing, assembling, maintenance and repair, or storage of material