How to clean up fire extinguisher residue

First, make sure the fire is out

• Watch the area for a while. Fires can re-ignite, especially in grease, upholstery and inside appliances.
• If the fire was larger than a wastebasket, reached the walls or cupboards, or you are unsure it is fully out, call 911 and have the fire department check.
• Ventilate the room.
• Replace or recharge the extinguisher. Once used, even briefly, it may not hold pressure.

Find out what was in the extinguisher

The label tells you the type. Cleanup depends on it.

Multipurpose dry chemical (ABC). The usual household extinguisher. The agent is a fine yellow or white powder, mainly monoammonium phosphate.

Regular dry chemical (BC). A white powder based on sodium bicarbonate or potassium bicarbonate.

Wet chemical (K). Found in commercial kitchens and some homes. A liquid that turns burning fat into a soapy foam.

Carbon dioxide. Leaves no residue.

Clean agent. A gas that leaves no residue. Used around electronics.

Water or foam. Leaves water, or a foam film.

Is the powder dangerous?

Dry chemical agents are considered low in toxicity, but they are irritants. The powder is very fine. Breathing it irritates the nose, throat and lungs, and it irritates eyes and skin. Anyone with asthma should stay out until it has been cleaned up. If someone has breathed in a lot and is coughing or short of breath, get medical advice.

Wear:

• A well-fitted dust mask or respirator
• Safety glasses or goggles
• Gloves and long sleeves

Keep children and pets out of the room.

Why speed matters with dry chemical

Monoammonium phosphate is mildly acidic. When it absorbs moisture from the air it becomes corrosive to metals. Left on a stove, in an appliance or inside electronics, it pits and corrodes surfaces and contacts. It also cakes when damp and becomes harder to remove. Aim to clean it up within a day or two.

The powder is fine enough to drift well beyond where it was sprayed. Expect to find it in adjoining rooms and inside cupboards.

Cleaning up dry chemical powder

1. Switch off the furnace or air conditioning fan so the powder is not drawn into the ducts. Replace the filter afterwards.
2. Vacuum the loose powder with a vacuum that has a HEPA filter. An ordinary vacuum can pass the finest powder through its filter and back into the air, and the powder is hard on the motor. A shop vacuum with a fine-particle filter is a second choice.
3. Do not sweep vigorously or use compressed air. Both put the powder into the air.
4. Do not wet it first. Water turns it into a paste.
5. Wipe hard surfaces with a damp cloth after vacuuming. For remaining film from an ABC extinguisher, a solution of baking soda in warm water helps neutralise the acidic residue. For BC powder, a little vinegar in warm water does the same job for its alkaline residue. Rinse with clean water and dry.
6. Wash dishes, pots and utensils that were exposed.
7. Launder clothing and fabrics. Shake or vacuum them outdoors first.
8. Vacuum carpets and upholstery slowly and repeatedly.

Sealed vacuum bags and used cloths can normally go in household waste. Check your municipality’s rules if you have a large quantity.

Food, appliances and electronics

Food. Throw out any food the powder touched and any that was open nearby. Unopened cans and jars can be washed.

The stove and oven. Clean thoroughly before use, including burners, drip pans and inside the oven. Powder left on an element burns and smells. If the fire was in the appliance, have it checked before using it again.

Small appliances. Powder gets drawn inside toasters, microwaves and anything with a fan or vents. If an appliance was running or directly sprayed, replacing it is often the practical answer.

Electronics. Do not switch on a computer, television or other device that has powder in it. Powder inside causes corrosion and overheating. Vacuuming the outside is not enough. Valuable equipment should go to a specialist.

The range hood. Check the filter and fan.

Wet chemical, foam and carbon dioxide

Wet chemical. Switch off the power to cooking appliances at the breaker before cleaning. Wear gloves and eye protection, because the agent is alkaline. Wipe up the foam and residue with hot soapy water, rinse well and dry.

Foam. Wipe up, wash with detergent, rinse and dry. Treat soaked materials as you would after any water spill.

Carbon dioxide and clean agents. No residue. Ventilate the room. What remains is the smoke damage from the fire.

Do not forget the smoke

The extinguisher residue is often the smaller problem. Even a brief fire leaves soot and odour on walls, ceilings and inside cupboards, and that needs its own cleaning. Dry soot comes off with dry methods before any wet washing.

When to call a professional

• The powder was drawn into the heating system
• It covered several rooms
• Electronics or expensive appliances were exposed
• There is smoke or heat damage as well
• Someone in the household has a respiratory condition

Insurance

Where the fire is an insured loss, cleaning up the extinguishing agent is normally part of the same claim, along with the smoke damage. Photograph the area before you start.

More: fire damage restoration.