The M256A1 detection kit is used to check for?

The M256A1 is used to detect and identify blood, blister and nerve agents present either as liquid or as vapor. It can also be used to determine when it is safe to unmask after a chemical or biological attack, and in locating and identifying chemical hazards.

This kits is not an alarm, but is instead used as a tool after soldiers or first responders have received other warnings about the possible presence of chemical or biological warfare agents, and have responded by putting on their chemical protective clothing.