Is Fire Extinguisher Powder Toxic?

Hector Alejandro/CC-BY-2.0

None of the three chemicals most commonly used in dry fire extinguishers is acutely toxic. One component, monoammonium phosphate, has the potential to cause minor skin irritation and is classed in the same category as acetone.

Most dry fire extinguishers use compressed nitrogen gas to propel a yellow fire-suppressing powder over the flames. This powder is made from sodium bicarbonate, also known as baking soda, a chemical closely related to potassium bicarbonate and monoammonium phosphate. Of these, only monoammonium phosphate has the potential to irritate skin. The National Fire Prevention Association has assigned monoammonium phosphate a health hazard rating of “1,” the lowest level given.