Choosing a Fire Extinguisher.

Did you know a home fire can double in size every 30 seconds? That means what started as a grease fire on your stove can burn out of control in under 3 minutes. In fact, it only takes 5-10 minutes for a two-story home to become totally engulfed in flames.

Having a fire extinguisher within easy reach can make all the difference!

Classes of Extinguishers

Typical Uses of Common Extinguishers

Helpful Hints

 

 

 

Extinguisher Classes


Class A fires are ordinary materials like burning paper, lumber, cardboard, plastics etc.


Class B fires involve flammable or combustible liquids such as gasoline, kerosene, and common organic solvents used in the laboratory.
 

Class C fires involve energized electrical equipment, such as appliances, switches, panel boxes, power tools, hot plates and stirrers. Water is a particularly dangerous extinguishing medium for class C fires because of the risk of electrical shock.

Class D fires involve combustible metals, such as magnesium, titanium, potassium and sodium as well as pyrophoric organometallic reagents such as alkyllithiums, Grignards and diethylzinc. These materials burn at high temperatures and will react violently with water, air, and/or other chemicals. Handle with care!!

Some fires may be a combination of these! Your fire extinguishers should have ABC ratings on them. These ratings will often have numbers on them that look something like "3-A:40-B:C". Higher numbers mean more firefighting power. In this example, the extinguisher has a good firefighting capacity for Class A, B and C fires.

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Here are typical uses for common extinguishers:

• Water extinguishers are suitable for class A (paper etc.) fires, but not for class B, C and D such as burning liquids, electrical fires or reactive metal fires. In these cases, the flames will be spread or the hazard made greater!

   

• Dry chemical extinguishers are useful for class ABC fires and are your best all around choice. They have an advantage over CO₂ extinguishers in that they leave a blanket of non-flammable material on the extinguished material which reduces the likelihood of re-ignition. They also make a terrible mess -- but if the choice is a fire or a mess, take the mess! Note that there are two kinds of dry chemical extinguishers!
   
  • Type BC fire extinguishers contain sodium or potassium bicarbonate.
  • Type ABC fire extinguishers contain ammonium phosphate.

   

• CO₂ (carbon dioxide) extinguishers are for class B and C fires. They don't work very well on class A fires because the material usually reignites. CO₂ extinguishers have an advantage over dry chemical in that they leave behind no harmful residue -- a good choice for an electrical fire on a computer or other delicate instrument. Note that CO₂ is a bad choice for a flammable metal fires such as Grignard reagents, alkyllithiums and sodium metal because CO₂ reacts with these materials. CO₂ extinguishers are not approved for class D fires!

   

• Metal/Sand Extinguishers are for flammable metals (class D fires) and work by simply smothering the fire. You should have an approved class D unit if you are working with flammable metals.
  
   
• Typical small lab fires (in a hood or on a bench) can easily be controlled by a dry chemical (ABC) or CO₂ extinguisher provided that you are properly trained.

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Helpful Hints:

Check out the potential fire hazards in your area.
Is there an extinguisher available?

Do you know how to operate it?

Are your extinguishers suitable for the fires you may encounter?

If not, you'll want to contact your local fire authority.

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