For a single exposure to sounds there has been a safe level vs exposure time guide made it states that if you are subjected to sounds of the following then you risk damage to your ear.
:-100db for 8 hours
:-112db for 20 min
:-126db for 1 min
:-144db for 1 sec
:-100db for 8 hours
:-112db for 20 min
:-126db for 1 min
:-144db for 1 sec