WHEN AIDED BY A RESPIRATOR, THE WEARER SHOULD BE THOROUGHLYFAMILIAR WITH THE RESPIRATOR'S OPERATION, AND NEEDED ADJUSTMENTS BEFORE AND ITS REQUIRED MAINTENANCE AFTER EACH USE. MAINTENANCE VARIES FOR DIFFERENT TYPES OF RESPIRATORS, AND THEMANUFACTURER'S INSTRUCTIONS SHOULD BE HEEDED IF OPTIMUM PERFORMANCE IS TO RESULT. THIS ARTICLE DISCUSSES PROCEDURES RECOMMENDED BY VARIOUS MANUFACTURERS OF RESPIRATORS INCLUDING THOSE FOR PARTICULATE FILTER AND CHEMICAL CARTRIDGE TYPES, AIR LINE RESPIRATORS, AND GAS MASKS. ALSO DISCUSSED ARE GUIDELINES FOR SELF-CONTAINED BREATHING APPARATUS (SCBA) USAGE IN COLD ENVIRONMENTS, AND NEW ANSI STANDARD ON SCBAS FOR FIRE FIGHTERS.