How do multi-class dry chemical fire extinguishers work?

If you ask any firefighter what it takes to create a fire, you will learn that you have to have three things:

  1. A fuel - some sort of combustible solid, liquid or gas
  2. Oxygen to react with the fuel
  3. Heat - there must be enough heat to get the fuel above its flash point. There is paper on your desk right now that is surrounded by oxygen. It does not burn unless you get the paper hot enough.

If you want to put out a fire, you need to remove one of the three elements. When you watch firefighters battling a forest fire, they generally try to remove fuel or heat. Either they pour water on the fire to reduce the temperature, or they try to bulldoze strips of bare earth to eliminate the fuel.

A carbon dioxide fire extinguisher works by eliminating oxygen and replacing it with carbon dioxide. You could do the same thing with just about any non-oxidizing gas (nitrogen, for example), however carbon dioxide is inexpensive and easy to store.

Another way to cut off oxygen is to throw a blanket over the fire. Covering the fire with dirt or sand does the same thing. You might have heard that you can put out a kitchen fire by throwing baking soda or salt on the fire. Throwing sand would do the same thing, however most people have more salt in their kitchens than they have sand.

Dry chemical fire extinguishers are by far the most common fire extinguishers in the home. They can handle all three types of fires you would find in a kitchen or workshop: combustible solids like wood or paper, combustible liquids like gasoline or grease, and electrical fires. The idea behind a dry chemical fire extinguisher is to blanket the fuel with an inert solid (similar to dirt or sand). A dry chemical extinguisher sprays a very fine power of sodium bicarbonate (normal baking soda), potassium bicarbonate (nearly identical to baking soda), or monoammonium phosphate. These solids coat the fuel and smother the fire.

For more information, read through our description of fire extinguisher types.

How do ionization smoke detectors work?

All smoke detectors consist of two basic parts: a sensor to sense the smoke and a very loud electronic horn to wake people up. Smoke detectors can run off of a 9-volt battery or 120-volt house current.
Ionization smoke detectors use an ionization chamber and a source of ionizing radiation to detect smoke. This type of smoke detector is more common because it is inexpensive and better at detecting the smaller amounts of smoke produced by flaming fires.

An ionization chamber is very simple. It consists of two plates with a voltage across them, along with a radioactive source of ionizing radiation, like this:
The alpha particles generated by the americium have the following property: They ionize the oxygen and nitrogen atoms of the air in the chamber. To "ionize" means to "knock an electron off of." When you knock an electron off of an atom, you end up with a free electron (with a negative charge) and an atom missing one electron (with a positive charge). The negative electron is attracted to the plate with a positive voltage, and the positive atom is attracted to the plate with a negative voltage (opposites attract, just like with magnets). The electronics in the smoke detector sense the small amount of electrical current that these electrons and ions moving toward the plates represent.

When smoke enters the ionization chamber, it disrupts this current -- the smoke particles attach to the ions and neutralize them. The smoke detector senses the drop in current between the plates and sets off the horn.

How often do my fire extinguishers need to be inspected?

Your fire extinguishers need to be inspected and certified once a year. This is to meet NFPA standards, your authority having jurisdiction's requirements, and the needs of some insurance companies.  

Annually, Macks Fire Protection will come to your location and provide this service. If your fire extinguishers need any other type of service such as a hydrostatic test or 6-year maintenance, our fire protection specialists will notify you and obtain permission to provide this additional work.  See our page on fire extinguishers for more information.

Why shouldn't I just buy new extinguishers every year instead of getting them certified?

One option is to simply purchase new fire extinguishers each year.  However, many times, the fire extinguishers sold on retail store shelves are of inferior quality to the ones that Macks Fire Protection provides. Our extinguishers have metal heads versus the plastic headed units found in stores. This allows for your extinguisher to be recharged if you use it (even for one little squeeze). Plastic headed extinguishers are designed to be disposable.

If you have a question on purchasing versus re-certification of your extinguisher, please call us or ask your fire protection specialist when he visits you.  We are here to inform and educate!

I've never used my extinguisher and the arrow is in the green. Is it still good?

That depends...on a lot of things.  While the gauge being in the green is a basic indicator of the life of the extinguisher, age, location, type of extinguisher, and many other factors dictate if your extinguisher will work in an emergency.

It is always better to be safe than sorry, so it is best to have a fire protection specialist provide a free safety inspection and analysis to let you know exactly the situation with your extinguishers. 

How do I use my fire extinguisher?


The basic, basic idea to remember is PASS--Pull, Aim, Squeeze, and Sweep.  We have a specific page dedicated to helping you understand how this vital little tool works.  Visit our Training Videos page to learn more.

Do you offer fire training classes or demonstrations?

Yes, we do.  Visit our Fire Training page for more information.