NIOSH Recommended Exposure Limit

A worker's exposure to sound of each intensity level shown in the table should not equal or exceed the duration shown in the table. Durations are calculated from the formula:

$An equation. T equals the fraction 480 over 2 to a power which is a fraction. The numerator is L minus 85 and the denominator is 3.$

where T is duration in minutes and L is exposure level in dBA.

Exposure Level (dBA)	Duration
Exposure Level (dBA)	Hours	Minutes	Seconds
80	25	24	0
81	20	10	0
82	16	0	0
83	12	42	0
84	10	5	0
85	8	0	0
86	6	21	0
87	5	2	0
88	4	0	0
89	3	10	0
90	2	31	0
91	2	0	0
92	1	35	0
93	1	16	0
94	1	0	0
95	—	47	37
96	—	37	48
97	—	30	0
98	—	23	49
99	—	18	59
100	—	15	0
101	—	11	54
102	—	9	27
103	—	7	30
104	—	5	57
105	—	4	43
106	—	3	45
107	—	2	59
108	—	2	22
109	—	1	53
110	—	1	29
111	—	1	11
112	—	—	56
113	—	—	45
114	—	—	35
115	—	—	28
116	—	—	22
117	—	—	18
118	—	—	14
119	—	—	11
120	—	—	9
121	—	—	7
122	—	—	6
123	—	—	4
124	—	—	3
125	—	—	3
126	—	—	2
127	—	—	1
128	—	—	1
129	—	—	1
130–140	—	—	less than 1

Source: U.S. Dept. of Health and Human Services. Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health.
Criteria for a Recommended Standard. Occupational Noise Exposure. Revised Criteria 1998.
Cincinnati (OH): June 1998.