When using water to extinguish a fire involving pesticides or a poison, the PRIMARY concern should be:

• A. Foam generation
• B. Thermal expansion of groundwater
• C. Air contamination
• D. Run-off contamination

Answer: (D)

When fighting a fire that involves pesticides or poisons, the biggest risk from using water is spreading the contaminant off the site. Many pesticides dissolve in water, and as you apply water to cool and extinguish the flames, that contaminated water can run off into nearby drainage systems, streams, and eventually surface water or groundwater. This creates environmental and public health hazards long after the fire is out. So the primary concern is preventing runoff contamination—containment, berms, and measures to minimize the amount of contaminated water leaving the scene.

Foam generation isn’t the main issue here, and while vapors and groundwater movement can be concerns in other contexts, the most critical risk during extinguishment is the potential for off-site contamination from runoff.