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Ask A Toxicologist > Are kitchen fire extinguishers (ABC-type) toxic?

Are kitchen fire extinguishers (ABC-type) toxic?

posted on 8:16 AM, March 4, 2016

ABC-type fire extiguishers, which are capable to put out fires composed of trash, wood, paper, liquids and electrical equipment, contain the chemicals monoammonium phosphate and ammonium sulfate. These compounds may have multiple uses, and they may be added to foods such as baking powders and breads to control acidity, and as a nutrient source to help bread rise. In this role they are recognized as safe by the United States Food and Drug Administration (FDA).

These chemicals may also be included as components in some fertilizers. Just as these chemicals control acidity in foods, they also control acidity in soil which helps plants grow.  In this role, these chemicals are also considered to be nonhazardous when used as directed. They can be combined with other substances to make fireproofing materials, which prevent fires because they do not burn, and to make flame retardant materials, which help prevent fires by slowing burning. They are also used as one of the substances in fire extinguishers, which are portable devices that help put out fires. When used in fire extinguishers, these two dry chemicals are used to coat surfaces involved in a fire, therefore helping to stop burning. When used as a component of fire retardant or fireproofing materials, these chemicals help to lower the temperature of the fire.

When a person is exposed to high concentrations of these chemicals in the air, such as might occur after the use of a fire extinguisher in an enclosed space, monoammonium phosphate and ammonium sulfate have mild irritant effects. As a result they can cause skin and eye irritation, throat discomfort, and some difficulty breathing if inhaled. These effects are usually short lived and go away on their own. If large amounts of these substances are swallowed, some nausea and vomiting can occur. In an incident reported to the Rocky Mountain Poison and Drug Center in Colorado, a group of children were exposed to monoammonium phosphate when several fire extinguishers were sprayed in a closed area of a school. This resulted in some mild breathing issues, irritated skin, and vomiting, all of which rapidly resolved after a short time spent in fresh air with no lasting consequences.

If the eyes or skin are exposed to monoammonium phosphate or ammonium sulfate, washing the skin, or rinsing the eyes (after removing any contact lenses) with water for about 10 to 15 minutes will remove these substances and help decrease any mild irritation. For difficulty breathing, leaving the area and moving to an area with fresh air typically resolves the symptoms. In the exceedingly rare event of persistent respiratory symptoms such as shortness of breath, wheezing, or coughing that does not get better after spending 20 minutes in fresh air, an examination by a healthcare provider may be needed. In general, after a fire extinguisher containing monoammonium phosphate and ammonium sulfate is used in a closed area, opening the windows, moving to fresh air, wiping down any surfaces with a wet cloth, and rinsing eyes and skin with water should prevent or relieve any mildly irritating effects.

References:

ABC Fire Extinguisher Material Safety Data Sheet.  Walter Kidde Portable Equipment Inc. Available online at: Kidde ABC Fire Extinguisher MSDS.  Accessed February 10, 2016.

Burdock GA. Encyclopedia of Food & Color Additives. 1st Edition. Boca Raton: CRC Press, 1996.

U.S. Department of Health and Human Services Food and Drug Administration.  Direct Food Substances Affirmed as Generally Recognized as Safe.  Available at: US FDA Food Substances Affirmed as Generally Recognized as Safe.  Accessed February 10, 2016.

Monoammonium phosphate.  Micromedex® Healthcare Series [Internet database].  Greenwood Village, Colorado: Thomson Micromedex.  Accessed February 10, 2016.