Alberta’s Occupational Health and Safety Code, 2009
In Alberta the maximum permitted exposure level is to work in a 85dB environment for 8 hours. For each increase of 3dB you are doubling the loudness, so you have to cut the exposure time in half for it to be safe.
EX) 88dB environment is safe to work in for 4 hours before it becomes unsafe. A 100dB environment is only safe to be exposed in for 15 minutes.