[wp_code id="209"] Operate breathing apparatus open circuit • Part 1 of 4 Operate Breathing Apparatus Open Circuit Foundations Purpose, hazardous atmospheres, components and pre-donning checks. Operate breathing apparatus open circuit begins with disciplined preparation. Before a firefighter or emergency service worker can safely don and operate a breathing apparatus set, they must understand its purpose, the hazards it protects against, and the checks that confirm it is ready for immediate…