A common question from safety coordinators is why two different solutions ship with these kits. The Bitrex Sensitivity Solution (0503) is used first, before the respirator goes on, to confirm the person can actually detect the bitter taste — establishing their threshold. The stronger Bitrex Fit Test Solution (0504) is then aerosolized around the mask during the exercises. If they don't taste it while wearing the respirator, the fit passes. Skipping the sensitivity step invalidates the whole test, so keep both on hand and replenish them separately as they run out.

Bitrex testing is well suited to N95s, half-mask respirators, and other filtering facepieces where a taste-based method is appropriate. It's non-toxic, easy to administer without specialized machinery, and works well for annual fit-testing cycles across larger crews.

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