In a contaminated situation, which items should be downed first?

In a contaminated situation, the most critical priority is to ensure that the aircrew can safely and effectively remove any contaminants that may be present. Therefore, downing the mask and blower unit first is essential because these items are directly responsible for the aircrew's ability to breathe clean air and protect against exposure.

The mask provides protection from inhaling harmful substances, while the blower unit aids in providing a continuous supply of clean air. By removing these items first, the crew can reduce the risk of exposure to contaminants. This choice reflects a clear understanding of the importance of maintaining respiratory safety in a contaminated environment.

The other options involve items that, while still important, may not provide immediate relief from hazard. For instance, protective gloves and a mask, while vital for protection, do not address the immediate need for clean air as effectively as the combination of the mask and blower unit. Similarly, downing a helmet and oxygen tank does not prioritize the immediate air purification needs that the mask and blower unit address.