Which mnemonic is used to help remember lighter-than-air gases for firefighters?

• A. Noble gas mnemonic
• B. Gas hazard acronym
• C. Air gas mnemonic
• D. 4H MEDIC ANNA

Answer: (D)

The concept here is remembering which gases will rise and collect in upper spaces because they are lighter than air. Firefighters use a quick mental cue to keep this in mind during scene assessment, detection, and ventilation planning. The phrase 4H MEDIC ANNA is a widely taught mnemonic that helps recall several lighter-than-air gases, so detectors and operations are focused toward the ceiling and other high spots where those gases may accumulate. This reminder supports safe scene handling, since these gases can travel along ceilings and into upper compartments, creating hidden hazards that require monitoring at higher elevations and appropriate ventilation or isolation strategies. The other options don’t correspond to a standard mnemonic used specifically to recall lighter-than-air gases.