In the standard order of the atmospheric tests, which test is performed first?

• A. Oxygen
• B. Toxins
• C. Combustible/Flammability
• D. All three are monitored simultaneously

Answer: (A)

Measuring oxygen first establishes a safe baseline and ensures that any subsequent readings for toxins or flammability are reliable. Many detection methods depend on a normal ambient oxygen level; if oxygen is depleted, not only is the environment hazardous, but readings for other gases can be skewed or the instruments may not function correctly. Once oxygen is confirmed at a safe level, the process can proceed to assess toxins and then flammability, in that order. The idea of monitoring all three at once isn’t the standard practice because safety and accuracy require sequential checks, allowing sensors to operate properly and readings to be interpreted correctly.