Disclosed is an in-line silencer for a clean room breathing apparatus which reduces noise transmitted to a user from an attached air blower. The clean room breathing apparatus includes a headgear assembly worn by the user and an air blower that supplies air to or exhausts air from the headgear assembly...http://www.google.com/patents/US5526805?utm_source=gb-gplus-sharePatent US5526805 - In-line silencer for clean room breathing apparatus
