Fire Safety - Know Your Classifications

Posted by Michael Tobias on January 8th, 2020

Fire Safety - Know Your Classifications

It only takes one spark to lead to deadly path of destruction. When dealing with fire it is important to know the type of fire it is because different fire causing properties will need different extinguishing methods or fire extinguishers.

Fire extinguishers have been around since 1818 when a British captain named George William Manby invented the modern fire extinguisher made from copper and capable of holding three gallons of the dry chemical - potassium carbonate and compressed air.

The United States classifies fire into five categories based on the properties of the fire - A, B, C, D, and K. Understanding each class is imperative to know how to extinguish the fire. If the wrong extinguishing method is used the results range from no effect on the fire to an explosion.

THE FIVE CLASSIFICATIONS OF FIRE

Class A  - Common Combustible Materials

The most common type of fire in the home or workplace is considered a Class A. These fires are usually caused by paper, wood, plastics, garbage and fabric. 

Water or monoammonium phosphate, the chemical compound commonly found in fire extinguishers, are best to extinguish Class A fires.

Class B  - Flammable Liquids and Gases

Class B fires are caused by oil, grease, paint, and solvents, and flammable gases - propane and methane. Sometimes a Class B fire will occur in a home, however this type are usually found in industrial settings.

When extinguishing a Class B fire, don’t use water - it could spread the fire by dispersing the flammable liquids. The best method to extinguish a Class B fire is to smother it or by  a chemical reaction.. 

In Class B you can use a monoammonium phosphate, just as in Class A or sodium bicarbonate to produce a chemical reaction to extinguish the fire.

Class C  - Live Electrical Sources

Electrical fires are known as Class C fires. They can occur in homes or industrial buildings. A plan of action is important to know in case of an electrical fire. The plan is two-fold.

1. Disconnect the power source for the fire.

2. Use a fire extinguisher that contains monoammonium phosphate or sodium bicarbonate (same as Class B).

Do not use water because the current and flow through the water and may electrocute someone.

Class D  - Combustible Metals

Even though combustible metal fire or Class D fire are the least common, they can be rapidly become very destructive.  These fires originate from titanium, potassium, magnesium, and aluminum.

Class D fires normally occur in laboratories and industrial settings. Never use water on Class C because it will only strengthen the fire. These fires need a certain fire extinguisher containing graphite in powder form and sodium chloride in granular form. Plus, special training on how to properly handle these chemicals.

Class K  - Commercial Cooking Equipment

Class K fires occur in the kitchen usually from grease, oil, bacon grease and other oils used in cooking, especially in commercial kitchens. Class K fire have a special extinguisher that are made for hotter burning oils.  

FINAL THOUGHTS

If you have questions or need further assistance contact a fire or sprinkler engineer.

AUTHOR’S BIO

Michael Tobias is the founder and principal of Chicago Engineers. He is a graduate of Georgia Tech class of 2004, with a Bachelor of Mechanical Engineering with honors. His innovative approach to MEP engineering comes from graduating GE’s Engineering Leadership Program, where he designed wind turbines and biofuel power plant engines. Michael’s passion within design is energy efficiency and green technology.