Annex 1 of NR-15 – Tolerance Limits for Continuous or Intermittent Noise

858 hours
867 hours
876 hours
885 hours
894 hours and 30 minutes
904 hours
913 hours and 30 minutes
923 hours
932 hours and 40 minutes
942 hours and 15 minutes
952 hours
961 hour and 45 minutes
981 hour and 15 minutes
1001 hour
10245 minutes
10435 minutes
10530 minutes
10625 minutes
10820 minutes
11015 minutes
11210 minutes
1148 minutes
1157 minutes
Maximum Permissible Daily Exposure

1. For the purpose of applying Tolerance Limits, Continuous or Intermittent Noise is defined as noise that is not impact noise.

2. Continuous or intermittent noise levels should be measured in decibels (dB) using a sound level meter operating on the “A” weighting circuit and slow response (SLOW) mode. Readings should be taken close to the worker’s ear.

3. Exposure times to noise levels should not exceed the tolerance limits set in the table of this annex.

4. For intermediate noise level values, the maximum permissible daily exposure corresponding to the next higher level will be considered.

5. Exposure to noise levels above 115 dB(A) is not allowed for individuals who are not adequately protected.

6. If there are two or more periods of exposure to noise of different levels during the workday, their combined effects must be considered, such that if the sum of the following fractions:

C1/T1 + C2/T2 + C3/T3 + … + Cn/Tn

exceeds one, the exposure is above the tolerance limit.

In the above equation, Cn indicates the total time the worker is exposed to a specific noise level, and Tn indicates the maximum permissible daily exposure to that level according to the table of this Annex.

7. Activities or operations that expose workers to continuous or intermittent noise levels above 115 dB(A) without adequate protection will pose a serious and imminent risk.