Which color of smoke is cited as a particularly dangerous sign at hazmat incidents?

• A. Green
• B. Black
• C. White
• D. Red

Answer: (A)

Color cues at hazmat incidents help responders quickly gauge the type of danger. Green smoke is cited as a particularly dangerous sign because it’s commonly associated with releases of chlorine or other toxic industrial gases. Chlorine is highly toxic, heavier than air, and it can linger in pockets near the ground, causing severe respiratory irritation and injury with even brief exposure. Seeing green smoke should trigger urgent protective actions: move people upwind, establish a safe perimeter, and call in a hazmat team with the proper PPE. White smoke often suggests steam or non-toxic gas, black smoke points to burning hydrocarbons with heat and toxic byproducts, and red smoke isn’t a standard indicator of a specific hazard, so these colors don’t carry the same immediate inhalation risk as green.