It is best, where possible, to avoid any unprotected exposure to sound pressure levels above 100 dBA and to use hearing protection when exposed to levels above 85 dBA if prolonged exposure is expected. Also, care should be taken to minimize direct exposure to impulsive noise, such as from gun fire. Damage to hearing from noise is cumulative and irreversible. The Occupational Safety and Health Administration (OSHA) has enacted regulations concerning permissible levels of noise exposure in work environments.