(By authority conferred on the director of the department of consumer and industry  
services by sections 14 and 24 of 1974 PA 154 and Executive Reorganization  
Orders Nos. 1996-1 and 1996-2, MCL 408.1014, 408.1024, 330.3101, and 445.2001)  
R 325.2401 Scope.  
Rule 1. These rules apply only to places of employment.  
History: 1979 AC; 2003 AACS.  
R 325.2402 General definitions.  
Rule 2. As used in these rules:  
(a) "Aerosol" means particulate matter suspended in air.  
(b) "Contaminant" means an airborne material capable of causing  
occupational disease or significant physiological disturbances to a person, and includes,  
but is not limited to, the substances listed in R 325.2413 to R 325.2419.  
(c) "Director" means the director of the department of consumer and industry  
services or the designee of the director.  
(d) "Employer" means an individual or type of organization which has in its  
employ 1 or more individuals performing services for it.  
(e) "Gas" means a normally formless fluid which occupies a space or enclosure  
and which can be changed to the liquid or solid state by the effect of increased pressure  
or decreased temperature, or both.  
(f) "Inert gas" means a gas or vapor which acts primarily as a simple asphyxiant  
without other significant physiological effect, recognizing that an inert gas may have  
flammable or explosive characteristics.  
(g) "Inert particulate" means an aerosol which does not produce significant  
organic disease or toxic effect in a lung-tissue reaction from any of the following:  
(i) The architecture of the air spaces remains intact.  
(ii) Collagen (scar tissue) is not formed to a significant extent.  
(iii) The tissue reaction is potentially reversible.  
(h) "Particulate matter" means fine solid or liquid particles.  
(i) "Physical agent" means a form of energy transmitted directly or through the  
air from the point of emission to the receiver.  
(j) "Vapor" means the gaseous state of a substance.  
History: 1979 AC; 2003 AACS.  
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R 325.2403 Definitions pertaining to contaminants.  
Rule 3. As used in these rules:  
(a) "Maximum allowable concentration" or "MAC" means the threshold limit  
value or the time-weighted average 8-hour airborne concentration of a contaminant  
to which a person may be safely exposed. R 325.2413 to R 325.2419, tables 1 to 7,  
refer to the MAC of a particular contaminant.  
(b) "Mg/M3" means milligrams of particulate per cubic meter of air.  
(c) "Mppcf" means millions of particulates per cubic foot of air based on impinger  
samples counted by light field microscopic techniques.  
(d) "Non-respirable atmosphere" means an atmosphere which contains  
insufficient oxygen, or an elevated level of contaminants, which may render a person  
incapable of self-rescue.  
(e) "Ppm" means parts of vapor or gas per million parts of air by volume at 25  
degrees Celsius and 760 millimeters of mercury pressure.  
(f) "Source" means a process or equipment which releases a contaminant into the  
air in concentrations exceeding the MAC.  
History: 1979 AC; 2003 AACS.  
R 325.2404 Definitions pertaining to noise.  
Rule 4. As used in these rules:  
(a) "Auditory protective equipment" means ear plugs, muffs, or other protective  
devices worn by an exposed person to attenuate airborne noise pressure in the ear  
(b) "Broad-band noise" means noise generally distributed throughout the sound  
frequency spectrum.  
(c) "Continuous noise" means an uninterrupted noise or more than 60 noises per  
(d) "dBA" means the airborne sound pressure level measured with the "A"  
weighting network of a sound level meter.  
(e) "Decibel" or "dB" means a dimensionless unit expressing the ratio of 2 sound  
quantities in logarithmic form, 1 of which quantities is a reference level of 0.0002  
(f) "Impact noise meter" means an instrument used for the measurement of peak  
sound pressures of impulse.  
(g) "Impulse noise" means a single noise or 60 or less noises per minute.  
(h) "Noise" means airborne sound in the frequency range from 20 to 20,000 hertz  
or cycles per second.  
(i) "Sound level meter" means an instrument, whose characteristics comply with  
those specified in the American standards association, standard S1.4-1961, used for  
the measurement of the airborne sound pressure level.  
History: 1979 AC; 2003 AACS.  
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R 325.2405 Definitions pertaining to respirators.  
Rule 5. As used in these rules:  
(a) "Atmosphere immediately dangerous to life or health" means  
nonrespirable atmosphere.  
(b) "Canister" means a container filled with air-purifying media to remove gases  
and vapors from air drawn through the container. The canister may also contain an  
aerosol filter to remove solid or liquid particulate matter.  
(c) "Cartridge" means a canister having reduced air-purifying capacity.  
(d) "Facepiece" means that portion of a respirator that is designed to make a  
gastight or dusttight fit with the face and includes the headbands, exhalation valves,  
and connections for an air-purifying device or respirable-gas source. A half-mask  
facepiece covers the wearer's nose and mouth. A full-mask facepiece covers the  
wearer's nose, mouth, and eyes.  
(e) "Filter" means a media used in a respirator to remove solid or liquid particulate  
matter from air drawn through the respirator.  
(f) "Respiratory protective equipment" means a device or system designed to  
protect the wearer from inhalation of unhealthful atmospheres.  
(g) "Respirator" means a type of respiratory protective equipment.  
History: 1979 AC; 2003 AACS.  
R 325.2410 Definitions pertaining to controls.  
Rule 10. As used in these rules:  
(a) "Control" means the limitation of worker exposure to contaminate levels not  
exceeding the MAC.  
(b) "Controlled process" means an arrangement of equipment to control the  
contaminant by means of suitable design measures.  
(c) "Enclosure" means a room, booth, or exhaust hood that confines  
contaminants at their sources.  
(d) "General ventilation" means the supply and removal of air from a space to dilute  
or remove contaminants.  
(e) "Local exhaust ventilation system" means an arrangement of exhaust hoods,  
ducts, and fans that removes air to control a contaminant at its source.  
(f) "Process space" means a tunnel, process equipment, shaft, or enclosed space.  
(g) "Supply ventilation system" means an arrangement of inlet openings or  
equipment to introduce outside air into the working environment.  
History: 1979 AC; 2003 AACS.  
R 325.2411 Contaminants; exposure; MACs.  
Rule 11. (1) An employer shall not allow the exposure of a person to  
concentrations of a contaminant in excess of the limit expressed by the contaminant's  
MAC as established in R 325.2412 to R 325.2419.  
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(2) An employer shall not allow the exposure of a person to a contaminant or  
combination of contaminants in concentrations which are hazardous or injurious to  
the person's health.  
History: 1979 AC; 2003 AACS.  
R 325.2412 Maximum allowable concentrations.  
Rule 12. (1) Maximum allowable concentrations of air contaminants based on a  
repeated 8-hour work day exposure are in tables 1 to 7 in R 325.2413 to R 325.2419.  
(2) A substance in tables 1 to 6 in R 325.2413 to R 325.2418, which is preceded  
by A, C, or S, is an especially hazardous contaminant and all of the following precautions  
shall be taken:  
(a) If the substance is preceded by "A," then the employer shall not allow a person  
or any part of his or her anatomy to be exposed to or come in contact with the  
substance by any respiratory, oral, or skin route.  
(b) If the substance is preceded by "C," then its MAC means the highest  
concentration at which an employer may allow a person to be exposed at any time.  
(c) If the substance is preceded by "S," then an employer shall provide necessary  
precautions against skin absorption of the contaminant by a person.  
History: 1979 AC; 2003 AACS.  
R 325.2413 Maximum allowable concentrations for substances A and B.  
Rule 13. Table 1 reads as follows:  
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History: 1979 AC; 2003 AACS.  
R 325.2414 Maximum allowable concentrations for substances C and D.  
Rule 14. Table 2 reads as follows:  
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History: 1979 AC; 2003 AACS.  
R 325.2415 Maximum allowable concentrations for substances E to H.  
Rule 15. Table 3 reads as follows:  
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History: 1979 AC; 2003 AACS.  
R 325.2416 Maximum allowable concentrations for substances I to M.  
Rule 16. Table 4 reads as follows:  
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