DEPARTMENT OF LABOR AND ECONOMIC OPPORTUNITY  
DIRECTOR’S OFFICE  
GENERAL INDUSTRY SAFETY AND HEALTH STANDARD  
(By authority conferred on the director of the department of labor and economic  
opportunity by sections 14, 16, 19, 21, and 24 of the Michigan occupational safety and  
health act, 1974 PA 154, MCL 408.1014, 408.1016, 408.1019, 408.1021, and 408.1024,  
and Executive Reorganization Order Nos. 1996-1, 1996-2, 2003-1, 2008-4, 2011-4, and  
2019-3, MCL 330.3101, 445.2001, 445.2011, 445.2025, 445.2030, and 125.1998)  
PART 301. AIR CONTAMINANTS FOR GENERAL INDUSTRY  
R 325.51101 Scope, application, and availability of standards.  
Rule 1. (1) These rules do not apply to the following types of employment:  
(a) Agriculture.  
(b) Domestic.  
(c) Mining.  
(d) Construction.  
(2) Exposure to air contaminants in construction work is covered by Construction Safety  
and Health Standard Part 601. Air Contaminants for Construction.”  
(3) The following Michigan Occupational Safety and Health Administration (MIOSHA)  
standards are referenced in these rules. Up to 5 copies of these standards may be  
obtained at no charge from the Michigan Department of Labor and Economic  
Opportunity, MIOSHA Regulatory Services Section, 530 West Allegan Street, P.O. Box  
30643, Lansing, Michigan, 48909-8143 or via the internet at the following website:  
www.michigan.gov/mioshastandards. For quantities greater than 5, the cost, as of the  
time of adoption of these rules, is 4 cents per page.  
(a) General Industry Safety and Health Standard Part 302. Vinyl Chloride,”  
R 325.51401 to R 325.51414.  
(b) General Industry Safety and Health Standard Part 303. Methylenedianiline (MDA)  
in General Industry,” R 325.50051 to R 325.50076.  
(c) General Industry and Construction Safety and Health Standard Part 304. “Ethylene  
Oxide,” R 325.51151 to R 325.51177.  
(d) Occupational Health Standard Part 305. “Asbestos for General Industry,”  
R 325.51311 to R 325.51312.  
(e) General Industry and Construction Safety and Health Standard Part 306.  
Formaldehyde,” R 325.51451 to R 325.51477.  
(f) General Industry and Construction Safety and Health Standard Part 307.  
Acrylonitrile,” R 325.51501 to R 325.51527.  
(g) General Industry and Construction Safety and Health Standard Part 308. “Inorganic  
Arsenic,” R 325.51601 to R 325.51628.  
Page 1  
(h) General Industry Safety and Health Standard Part 309. “Cadmium in General  
Industry,” R 325.51851 to R 325.51886.  
(i) General Industry Safety and Health Standard Part 310. “Lead in General Industry,”  
R 325.51901 to R 325.51958.  
(j) General Industry and Construction Safety and Health Standard Part 311. “Benzene,”  
R 325.77101 to R 325.77115.  
(k) Occupational Health Standard Part 312. “1,3-Butadiene,” R 325.50091 to  
R 325.50093.  
(l) Occupational Health Standard Part 313. “Methylene Chloride,” R 325.51651 to  
R 325.51653.  
(m) General Industry and Construction Safety and Health Standard Part 314. “Coke  
Oven Emissions,” R 325.50100 to R 325.50136.  
(n) Occupational Health Standard Part 315. “Chromium (VI) in General Industry,”  
R 325.50141 to R 325.50143.  
(o) General Industry Safety and Health Standard Part 340. “Beryllium,R 325.34001  
to R 325.34010.  
(p) General Industry Safety and Health Standard Part 350. “Carcinogens,”  
R 325.35001 to R 325.35011.  
(q) Occupational Health Standard Part 451. “Respiratory Protection,” R 325.60051 to  
R 325.60052.  
(r) General Industry Safety and Health Standard Part 590. “Silica in General Industry,”  
R 325.59001 to R 325.59015.  
(s) Construction Safety and Health Standard Part 601. “Air Contaminants for  
Construction,” R 325.60151 to R 325.60161.  
History: 1990 AACS; 2013 AACS; 2017 AACS; 2019 AACS.  
R 325.51101a Rescinded.  
History: 2013 AACS; 2017 AACS; 2019 AACS.  
R 325.51102 Definitions.  
Rule 2. (1) "Ceiling" means the employee's exposure that shall not be exceeded during  
any part of the workday. If instantaneous monitoring is not feasible, then the ceiling shall  
be assessed as a 15-minute, time-weighted average exposure that shall not be exceeded  
during any part of the working day.  
(2) "Skin designation" means those substances so indicated that have toxic effects due  
to absorption through an employee's skin.  
(3) "Short-term exposure limit (STEL)" means the employee's 15-minute, time-  
weighted average exposure that shall not be exceeded at any time during a workday,  
unless another time limit is specified in a parenthetical notation below the limit. If  
another time period is specified, then the time-weighted average exposure over that time  
limit shall not be exceeded at any time during the workday.  
(4) "Time-weighted average (TWA)" means the employee's average airborne exposure  
in any 8-hour workshift of a 40-hour workweek that shall not be exceeded.  
Page 2  
(5) The terms "substance" and "air contaminant" are equivalent in meaning for purposes  
of these rules.  
History: 1990 AACS; 2001 AACS; 2017 AACS.  
R 325.51103 Exposure limits.  
Rule 3. An employer shall ensure that an employee exposure to any substance listed in  
tables G-1-A or G-2 in R 325.51108 is limited in accordance with the requirements of all  
of the following provisions:  
(a) With respect to table G-1-A, all of the following provisions apply:  
(i) Removed (May 9, 2001).  
(ii) Removed (May 20, 2001).  
(iii) An employee's exposure to any substance listed in table G-1-A shall not exceed the  
time-weighted average (TWA) limit, short-term exposure limit (STEL) and ceiling limit  
specified for that substance in table G-1-A.  
(iv) To prevent or reduce skin absorption, an employee's skin exposure to substances  
listed in table G-1-A with an "X" in the skin designation column following the substance  
name shall be prevented or reduced to the extent necessary through the use of gloves,  
coveralls, goggles, or other appropriate personal protective equipment, engineering  
controls, or work practices.  
(v) An employee shall not be exposed to air concentrations between the TWA and  
STEL limits more than 4 times in a workshift and such exposures shall be no less than 60  
minutes apart.  
(b) With respect to table G-2, all of the following provisions apply:  
(i) An employee's exposure to any substance listed in table G-2 in any 8-hour workshift  
of a 40-hour workweek shall not exceed the 8-hour, time-weighted average limit given  
for that substance in table G-2.  
(ii) An employee's exposure to a substance listed in table G-2 shall not exceed, at any  
time during an 8-hour workshift, the acceptable ceiling concentration limit given for the  
substance in the table, except for a period of time and up to a concentration that does not  
exceed the maximum duration and concentration allowed in the column under  
"Acceptable maximum peak above the ceiling concentration for an 8-hour workshift."  
For example, during an 8-hour workshift, an employee may be exposed to a  
concentration of Substance A (with a 10 parts of the substance per million parts of air  
(ppm) TWA, 25 ppm ceiling and 50 ppm peak) above 25 ppm (but not above 50 ppm)  
only for a maximum period of 10 minutes. Such an exposure shall be compensated for by  
exposures to concentrations less than 10 ppm so the cumulative exposure for the entire 8-  
hour workshift does not exceed a time-weighted average of 10 ppm.  
(iii) If a substance is preceded by an "S", then an employer shall take the necessary  
precautions to prevent an employee from absorbing the substance through his or her skin.  
History: 1990 AACS; 2001 AACS; 2017 AACS.  
R 325.51104 Computation formulae.  
Page 3  
Rule 4. The computation formulas that apply to employee exposure to 1 or more  
substances that have an 8-hour, time-weighted average listed in table G-1-A or G-2 to  
determine whether an employee is exposed in excess of the exposure limit are as follows:  
(a) An employer shall compute the cumulative exposure for multiple exposures to a  
single substance for an 8-hour workshift as follows:  
E = (C1T1 + C2T2 + ... CnTn) ÷ 8 hours  
Where:  
E is the cumulative exposure for an 8-hour workshift.  
C1 is the substance concentration during the first period of time "T" where the  
concentration remains constant.  
C2 is the substance concentration during the second period of time "T" where the  
concentration remains constant.  
T is the period of time in hours for which the substance concentration C remains  
constant.  
The value of E shall not exceed the 8-hour, time-weighted average limit for the  
substance as specified in table G-1-A or G-2.  
To illustrate the formula for a cumulative exposure to a single substance, assume that  
Substance A has an 8-hour, time-weighted average exposure limit of 100 ppm noted in  
table G-1-A. Assume that an employee is subject to the following exposures over an 8-  
hour workshift:  
Two hours' exposure at 150 ppm  
Two hours' exposure at 75 ppm  
Four hours' exposure at 50 ppm  
Substituting this information into the formula:  
E = [(150 ppm X 2 hrs) + (75 ppm X 2 hrs) + (50 ppm X 4 hrs)] ÷ 8 hrs  
E = [300 ppm·hrs + 150 ppm·hrs + 200 ppm·hrs] ÷ 8 hrs  
E = 650 ppm·hrs ÷ 8 hrs = 81.25 ppm  
Since the cumulative exposure of 81.25 ppm is less than the exposure limit of 100 ppm,  
then the employee's 8-hour workshift exposure is acceptable.  
(b) An employer shall compute the equivalent exposure for a mixture of air  
contaminants for an 8-hour workshift as follows:  
Em = (C1 ÷ L1 + C2 ÷ L2) + ... (Cn ÷ Ln)  
Where:  
Em is the equivalent exposure to the mixture of air contaminants during an 8-hour  
workshift.  
C1 is the average 8-hour concentration of the first substance.  
Page 4  
C2 is the average 8-hour concentration of the second substance.  
L is the 8-hour, TWA exposure limit for that particular substance. The value of Em  
shall not exceed a value of one (1.0).  
To illustrate the formula for a mixture of air contaminants, assume the following  
exposures:  
Average concentration of 8-hour 8-hour TWA exposure  
Substances in mixture  
exposure (C)  
500 ppm  
limit (L)  
Substance A  
Substance B  
Substance D  
1,000 ppm  
45 ppm  
40 ppm  
200 ppm  
200 ppm  
Substituting this information into the formula:  
EM = (500 ppm ÷ 1,000 ppm) + (45 ppm ÷ 200 ppm) + (40 ppm ÷ 200 ppm)  
Em = 0.500 + 0.225 + 0.200  
Em = 0.925  
Since the value of Em did not exceed one (1.0), the employee's 8-hour workshift  
exposure to the mixture of air contaminants is acceptable.  
History: 1990 AACS; 2001 AACS; 2017 AACS.  
R 325.51105 Methods of compliance.  
Rule 5. To achieve compliance with the provisions of R 325.51103 and R 325.51104,  
administrative or engineering controls must first be determined and implemented if  
feasible. If such controls are not feasible to achieve full compliance, then personal  
protective equipment or any other protective measures must be used to keep the  
employee’s exposure to air contaminants within the exposure limits prescribed in these  
rules. Any equipment and technical measures used for this purpose must be approved for  
each particular use by a competent industrial hygienist or other technically qualified  
person. If a respirator is used, its use must comply with the provisions of Occupational  
Health Standard Part 451. “Respiratory Protection.”  
History: 1990 AACS; 2001 AACS; 2013 AACS; 2019 AACS.  
R 325.51106 Rescinded.  
History: 1990 AACS; 2001 AACS.  
Page 5  
R 325.51107 Stay of enforcement.  
Rule 7. Enforcement of the limits are indefinitely stayed for the following  
substances until the United States department of labor, occupational safety and  
health administration (OSHA) publishes in the Federal Register a notice that a  
sampling and analytical technique is available:  
(a) Aluminum alkyls.  
(b) Ethylidine norbornene.  
(c) Hexafluoroacetone.  
(d) Mercury (alkyl compounds).  
(e) Oxygen difluoride.  
(f) Phenylphosphine.  
(g) Sulfur pentafluoride.  
History: 1990 AACS.  
Page 6  
R 325.51108 Tables.  
Rule 8. Tables G-1-A and G-2 read as follows:  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
Abate  
100  
10  
15  
180  
25  
150  
270  
5
Acetaldehyde  
Acetic acid  
Acetic anhydride  
Acetone  
75-07-0  
64-19-7  
108-24-7  
67-64-1  
75-05-8  
20  
750  
40  
1800  
70  
1000  
60  
2400  
105  
Acetonitrile  
2-Acetylaminofluorine; see GI Part 350.  
CarcinogensF  
53-96-3  
Acetylene dichloride; see 1,2-Dichloroethylene  
Acetylene tetrabromide  
Acetylsalicylic acid (Aspirin)  
Acrolein  
79-27-6  
50-78-2  
107-02-8  
79-06-1  
79-10-7  
1
14  
5
x
x
0.1  
0.25  
0.03  
30  
0.3  
0.8  
Acrylamide  
Acrylic acid  
10  
Acrylonitrile; see GI & CS Part 307. AcrylonitrileF  
107-13-1  
2
4.34  
10  
21.7  
Page 7  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
Aldrin  
309-00-2  
107-18-6  
107-05-1  
106-92-3  
2179-59-1  
2
1
5
2
0.25  
5
4
x
x
Allyl alcohol  
Allyl chloride  
10  
6
3
2
Allyl glycidyl ether (AGE)  
Allyl propyl disulfide  
22  
12  
10  
3
44  
18  
α Alumina (aluminum oxide)  
Respirable fraction  
Total dust  
1344-28-1  
5
10  
Aluminum (as Al)  
Alkyls  
2
Metal  
Respirable dust  
Total dust  
Pyro powders  
Soluble salts  
Welding fumes*  
5
15  
5
2
5
7429-90-5  
92-67-1  
4-Aminodiphenyl; see GI Part 350. CarcinogensF  
2-Aminoethanol; see Ethanolamine  
2-Aminopyridine  
Amitrole  
504-29-0  
61-82-5  
0.5  
2
0.2  
Ammonia  
7664-41-7  
35  
24  
Page 8  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
Ammonium chloride fume  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
12125-02-9  
10  
20  
Ammonium sulfamate  
Respirable dust  
Total dust  
7773-06-0  
5
10  
n-Amyl acetate  
628-63-7  
626-38-0  
62-53-3  
100  
125  
2
525  
650  
8
x
x
sec-Amyl acetate  
Aniline and homologues  
Anisidine (o- and p-isomers)  
Antimony and compounds (as Sb)  
ANTU (alpha-naphthylthiourea)  
Arsenic, organic compounds (as As)  
29191-52-4  
7440-36-0  
86-88-4  
0.5  
0.5  
0.3  
0.5  
7440-38-2  
Arsenic, inorganic compounds (as As); see GI &  
CS Part 308. Inorganic ArsenicF  
7440-38-2  
7784-42-1  
0.01  
0.2  
Arsine  
0.05  
TWA  
STELD  
Asbestos; see OH Part 305. Asbestos for General  
IndustryF  
Varies  
0.1f/cc  
mg/m3C  
Skin  
Designation  
ppmB  
ppmB  
mg/m3C  
ppmB mg/m3C  
Atrazine  
1912-24-9  
5
Page 9  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
Azinphos-methyl  
86-50-0  
0.2  
0.5  
x
Barium, soluble compounds (as Ba)  
7440-39-3  
Barium sulfate  
Respirable dust  
Total dust  
7727-43-7  
5
10  
Benomyl  
Respirable dust  
Total dust  
17804-35-2  
5
10  
BenzeneE; see GI & CS Part 311. BenzeneF and  
table G-2 for limits applicable in the operations  
or sectors excluded in R 325.77101E  
71-43-2  
92-87-5  
1
3.19  
5
15.97  
Benzidine; see GI Part 350. CarcinogensF  
p-Benzoquinone; see Quinone  
Benzo(a)pyrene; see Coal tar pitch volatiles  
Benzoyl peroxide  
Benzyl chloride  
94-36-0  
5
5
100-44-7  
1
0.0002  
0.002  
(0.2 μg/m3)  
(2.0 μg/m3)  
Beryllium and beryllium compounds (as Be) see  
GI Part 340. Beryllium  
7440-41-7  
Page 10  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
Biphenyl; see Diphenyl  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
Bismuth telluride, Undoped  
Respirable dust  
1304-82-1  
5
15  
Total dust  
Bismuth telluride, Se-doped  
5
Borates, Tetra, Sodium Salts  
Anhydrous  
1330-43-4  
1303-96-4  
12179-04-3  
10  
10  
10  
Decahydrate  
Pentahydrate  
Boron oxide, Total dust  
Boron tribromide  
Boron trifluoride  
Bromacil  
1303-86-2  
10294-33-4  
7637-07-2  
314-40-9  
10  
2
1
1
10  
3
1
10  
0.7  
0.7  
5
Bromine  
7726-95-6  
7789-30-2  
75-25-2  
0.1  
0.1  
0.5  
0.3  
Bromine pentafluoride  
Bromoform  
1,3-Butadiene; see OH Part 312. 1,3-ButadieneF  
106-99-0  
106-97-8  
1
2.2  
5
11.1  
Butane  
800  
1900  
Butanethiol; see Butyl mercaptan  
Page 11  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
CAS No.A  
ppmB  
ppmB  
ppmB mg/m3C  
2-Butanone (Methyl ethyl ketone)  
2-Butoxyethanol  
78-93-3  
111-76-2  
123-86-4  
105-46-4  
540-88-5  
141-32-2  
71-36-3  
200  
25  
590  
120  
710  
950  
950  
55  
300  
885  
x
x
x
n-Butyl acetate  
150  
200  
200  
10  
200  
950  
sec-Butyl acetate  
tert-Butyl acetate  
Butyl acrylate  
nButyl alcohol (n-butanol)  
sec-Butyl alcohol (sec-butanol)  
tert-Butyl alcohol (tert-butanol)  
Butylamine  
50  
150  
78-92-2  
100  
100  
305  
300  
75-65-0  
150  
450  
109-73-9  
5
15  
0.005  
tert-Butyl chromate (as Cr+6); see OH Part 315.  
Chromium (VI) in General IndustryF,G  
1189-85-1  
(5 μg/m3)  
x
n-Butyl glycidyl ether (BGE)  
n-Butyl lactate  
2426-08-6  
138-22-7  
109-79-5  
89-72-5  
25  
5
135  
25  
x
Butyl mercaptan  
0.5  
5
1.5  
30  
o-sec-Butylphenol  
p-tert-Butyltoluene  
98-51-1  
10  
60  
20  
120  
Page 12  
TABLE G-1-A. EXPOSURE LIMITS FOR AIR CONTAMINANTS  
TWA  
STELD  
mg/m3C mg/m3C  
Ceiling  
Skin  
Designation  
Substance  
CAS No.A  
7440-43-9  
ppmB  
ppmB  
ppmB mg/m3C  
Cadmium; see GI Part 309. Cadmium in General  
IndustryF  
0.005  
Calcium carbonate,  
Respirable dust  
Total dust  
1317-65-3  
5
15  
Calcium cyanamide  
Calcium hydroxide  
Calcium oxide  
156-62-7  
1305-62-0  
1305-78-8  
0.5  
5
5
Calcium silicate,  
Respirable dust  
Total dust  
1344-95-2  
5
15  
Calcium sulfate,  
Respirable dust  
Total dust  
7778-18-9  
76-22-2  
5
15  
Camphor, synthetic  
2
Caprolactam,  
Dust  
105-60-2  
5
1
20  
10  
3
40  
Vapor  
Captafol (DifolatanR)  
2425-06-1  
133-06-2  
63-25-2  
0.1  
5
Captan  
Carbaryl (SevinR)  
Carbofuran (FuradanR)  
5
1563-66-2  
0.1  
Page 13