While fire extinguishers do a great job of putting out small fires, it is an unfortunate fact that they can also be hazardous to your health.
The Fire Triangle
The Fire Triangle is also called the combustion triangle. There are three parts to the triangle required for a fire to ignite. These include:
- Oxidizing Agent (usual oxygen)
Additionally, a chain reaction is necessary to combine these elements and ignite a fire. If one or more of these parts are removed or blocked, a fire will either not start or be put out. Portable fire extinguishers serve to disrupt this process, depending on their suppressant type.
Different Types Of Fire Suppressants
There different types of extinguishers that use different suppressants. The goal of these is to remove the heat and/or oxygen from the fire and disrupt the chemical reaction that started it. These extinguishers have one of the following propellant sprays:
- Carbon Dioxide
- Dry Chemical Powder
- Wet Chemical
- Clean Agent
- Water / Foam
- Water Mist
- Halotron or Halon (no longer made for fire extinguishers)
A color-coded label should be present on the fire extinguisher that declares the class of fire for which it is meant for. Do not use a fire extinguisher if you are not clear what type of fire it can suppress.
Dry Chemical Fire Extinguishers
Dry chemical fire extinguishers extinguish the fire primarily by interrupting the chemical reaction of the fire triangle.
Today’s most widely used type of fire extinguisher is the multipurpose dry chemical that is effective on Class A, B, and C fires. These work by creating a barrier between the oxygen element and the fuel element in Class A fires. These are sprayed as a chemical powder.
Ordinary dry chemical fire extinguishers are for Class B & C fires only. It is important to use the correct extinguisher for the type of fuel! Using the incorrect agent can allow the fire to re-ignite after apparently being extinguished successfully.
Multi-Purpose Dry Chemical Extinguishers
The multi-purpose dry chemical fire extinguisher is the most commonly used fire extinguisher today. You can find them in offices, garages, and inside homes. They are effective against Class A, B, and C fires.
Like other types of fire extinguishers, dry powder fire extinguishers are usually red in color. They should also have the words DRY POWDER visibly posted on the side.
Class A, B, And C Fires
Here is a short run-down of class A, B, and C fires that a multi-purpose chemical fire extinguisher can put out:
Class A fires – involve common ordinary combustible materials such as wood, paper, rubber and some plastics.
Class B fires – involve flammable liquids, oils, tars, oil-based paints and gases.
Class C fires – involve charged electrical equipment.
Interrupting the Chemical Reaction
Dry chemical fire extinguishers work to put out fires mainly by interrupting the chemical reaction of the fire. It does this by forming a barrier between the fuel and oxygen elements.
Some chemical fire extinguishers are limited only to Class B & C fires. These are ordinary chemical fire extinguishers.
Make sure to select the correct extinguisher for you needs by checking the labeling before buying it. The wrong fire extinguisher will not be able to fully put a fire out and may allow it to reignite after you have fully spent the extinguisher!
Specialist Dry Powder Extinguishers
Class D fires require a specialist dry powder extinguisher to put out. These types of fires burn hot and spread easily and include metals such as magnesium, lithium, and crusty metal particles or shavings.
Specialist dry powder extinguishers are best used in industrial facilities where grinding, cutting, and welding take place. These fires need to be put out quickly so as not to ignite other objects or chemicals in the nearby area.
Specialist dry powder extinguishers work in a way similar to multi-purpose dry chemical extinguishers. They extinguish the fire by removing the heat from the fire or by separating the fuel from the oxygen.
However, Specialist dry powder extinguishers are only effective on Class D fires, and no other type.
Chemical Components Of Fire Extinguisher Powder
Powdered fire extinguishers include the following chemical ingredients:
- Mono ammonium phosphate (Class A, B, and C fires)
- Sodium bicarbonate (Class B and C fires)
- Magnesium aluminum silicate (Class A, B, and C fires)
- Copper metal (Class D fires)
- Sodium chloride (Class D fires)
- Sand (Class D fires)
- Muscovite mica
Also included in the mix is Nitrogen as a propellant.
What Happens If I get Fire Extinguisher Powder On Me?
Fire extinguisher powder is a major skin and eye irritant. It is non-toxic but can have health affects.
Exposure of the eyes or skin to any of the dry chemical fire extinguishers should be treated by immediate rinsing of the affected areas. After this initial treatment has been performed, call a doctor or visit the hospital to make sure no other problems arise.
Symptoms of nausea or vomiting may occur if the powder enters the body through the skin or inhalation. Breathing can also be made difficult and lead to coughing. People with lung conditions like asthma can have more serious respiratory effects if they inhale the powder and should seek medical attention soon after.
Since the chemicals are mostly non-toxic in small amounts, having contact with them will cause symptoms that can improve after rinsing the affected area.
Dry powder fire extinguishers can leave dust residue behind after they are used. It is important to clean the area of any of this to make sure you do not breathe it in or it does not get onto your skin.
If you have inhaled spray powder from a fire extinguisher, get to fresh air immediately.
Is It OK To Spray Someone With A Fire Extinguisher?
Spraying someone with a fire extinguisher can result in respiratory and eye damage. Additional skin and throat symptoms may result which can be painful and take time to recover from. Fire extinguishers are not designed to spray human beings directly and should not be used unless that person is on fire themselves. If a person requires the use of a fire extinguisher to put out a fire that has consumed them, the user should avoid spraying their facial area. In summary, it is only OK to spray someone with a fire extinguisher in an emergency where the person is actually on fire.
How Do You Clean Up Fire Extinguisher Powder?
Cleaning up fire extinguisher powder is easy and does not require a long process or special equipment. This is due to the types of chemicals used in the powder.
Mono ammonium phosphate, used in Class A, B, and C fire extinguishers, is a dry powder that sits atop objects as a dust particle. It is non-conductive to electricity, so will not react to nearby outlets or wires. It is corrosive, so if left will lead to the breakdown of materials it touches and must be cleaned up not long after extinguishing the fire.
Another chemical, sodium bicarbonate is a nontoxic and noncorrosive dry chemical that only needs minimal cleanup.
Potassium bicarbonate is a dry chemical that is also non-conductive and non-corrosive. It too is easily cleaned after the fire is extinguished.
Fire Extinguisher Yellow Powder – What Is It?
The fine yellow powder is released by multi-purpose dry chemical fire extinguishers. This color is due to the mono ammonium phosphate. A bonus of the yellow color is it helps to distinguish it from other non-multipurpose extinguishers.
Ordinary chemical fire extinguishers do not produce a yellow powder. This is because they use sodium bicarbonate (baking soda) and it comes out as a white powder.
Can You Use A BBQ After Spraying It With A Fire Extinguisher?
If a bbq gets enflamed to the extent that it requires the use of a fire extinguisher to put it out, it is recommended to clean the BBQ before using it again.
There could be residual fire extinguisher chemicals left on the grill that could get into any newly cooked food. Even though the powder is non-toxic in small amounts, it could affect the food taste and cause throat and stomach irritation.
The bbq may thus require a full cleaning and scraping to remove this residue. Any food that was hit by the fire extinguisher powder should also not be eaten.
While fire extinguisher powder can be hazardous to your health, you can mitigate these risks if you use one properly. Always follow all safety instructions when preparing for using a fire extinguisher in your home, office, or industrial facility.
Nick Klamecki is a certified Fire and Workplace Safety expert with 15 years experience in product research and testing. He has a degree in Economics from U.C. Davis, is an active outdoorsman and spent years ensuring the safety of special needs children. Nick researches and tests workplace, industrial and safety products and provides advice on their safe use.