Protective respirator masks currently being issued to Department employees are designed to protect the employee. Several different types of canister filters are currently being used by the Department. Employees shall be aware of the specific type of canister filter they are using and their limitations. Concerned Department members should understand the filtering capacity and the limitation of the mask being used. The filtering element of any mask creates a resistance to normal breathing efficiency. Prolonged periods of strenuous activity while wearing the mask will hasten fatigue.