Fire extinguishers are designed to put out or control small fires. A small or ‘incipient’ fire, if not checked immediately, will soon spread out of control. In fact, most big fires start out as small ones. It is important, therefore, that you equip your workplace with the proper fire extinguishers as part of your fire protection plan. It’s also the law. For a fire extinguisher to be effective, the following conditions must be met:

• The extinguisher must be right for the type of fire;
• it must be located where it can be easily reached;
• it must be in good working order;
• the fire must be discovered while it is still small;
• the person using the extinguisher must be trained to use it properly.

This guideline discusses fire extinguishing methods, types of extinguishers and their proper selection, location, identification, maintenance and use. It also covers employee training and outlines  requirements for extinguishers in workplaces.

Fire Extinguishing Methods

Fires can be extinguished in one or four ways:

1. By cooling: Water is used to cool the burning material below the temperature at which it starts to burn.
2. By smothering: Carbon dioxide (CO2) or foaming agents are used to smother the burning material so that air is excluded.
3. By removing the fuel: This is usually very difficult to do. An example is turning off a fuel line.
4. By disrupting the chemical chain reaction or interrupting the flame: Dry chemicals or halon are used to do this.

Types of Extinguishers

To help in choosing the proper extinguisher, fires are classed A, B, C, or D, according to the type of fuel (e.g., paper, grease, oil) that is involved in the fire. Extinguishers are available for use on one or more classes of fire, depending on the extinguishing agent they contain (e.g., water, chemicals). Figure 1 will help you to match types of extinguishers to different classes of fire.

Some extinguishers are suitable for one class of fire only; others can fight two or even three classes of fire. However, no extinguisher will fight all four classes of fire. Figure 2 gives examples of specific types of fire extinguishers, how they work, and the class(es) of fire on which they can be used.

Selection

Using the wrong extinguisher to fight a fire can have serious results. For example, if a water-based extinguisher is used on a flammable liquid fire (Class B fire), the fire may flare up, spread, and cause personal injury to the user and others. If a water-based extinguisher is used to fight a fire in or near electrical equipment (Class C fire), the user could suffer an electric shock.

Follow these steps in selecting extinguishers for your workplace:

• Conduct an assessment to identify your fire hazards and determine the type of extinguishers needed. The extinguishers you select must match the classes of fire most likely to occur. Remember to check your material safety data sheets to identify materials that could catch fire. The section on fire fighting measures give information on the type of extinguishing agent needed to put out a fire involving the material.

• Determine the size of potential fires in each area and how fast they could spread. Extinguishers for Class A and Class B fires are rated for the size of fire they can handle. This rating appears on the label and is expressed as a number from 1 to 40 for Class A fires and 1 to 640 for Class B fires. The higher the number, the larger the fire the extinguisher can put out. However, the higher the rating, the heavier the extinguisher. Extinguishers rated 2A:10B:C are suitable for home or office fires. Extinguishers for Class C fires depend upon such factors as the size of the electrical equipment, how it is constructed, whether it is enclosed, and the nature of the other combustible materials in the area. Agents for Class D fires should be carefully selected based on information in the material safety data sheet and the manufacturer’s recommendations. The amount of agent needed depends on the surface area of the metal, and its shape and form. (Contact JB Safety & Rescue Services to determine the number of fire extinguishers you need for your workplace.)

Consider other factors that affect selection:

• Possible health and safety hazards from chemical reactions between the extinguishing agent and the burning materials, or when using certain types of extinguishers in unventilated areas. Extinguishers with long-range nozzles, for example, are available for use in confined spaces or other hazardous areas.

• Atmospheric conditions in areas where extinguishers are located. Extreme cold, for example, could make water-based extinguishers ineffective. Where there may be corrosive fumes, select fire extinguishers that can resist corrosion, or provide protection against corrosion.

• Physical abilities of the user. The size and weight of extinguishers should match the physical abilities of those who have to use them. Extinguishers shouldn’t be too heavy for employees to handle.

Make sure that your extinguishers:

• are approved by a recognized laboratory and labeled as such;
• do not contain carbon tetrachloride, methyl bromide, or other toxic vaporizing liquids.

And lastly, do a reassessment whenever you make changes in your workplace, e.g., when you change a work process or the materials you are using.

Identification

Manufacturers place markings on extinguishers to indicate the class or classes of fire for which they are suitable. To make identification easier in an emergency, consider applying class ratings to wall panels near extinguishers. There markings should be easy to see from a distance of 4.6m (15 ft.).

One marking system uses letters, symbols and colors (see Figure 5). Another marking system uses pictures which show both the uses and non-uses of the extinguisher. This marking system is illustrated in Figure 6. Pictures give more information, but employees will need training to be able to recognize and understand them. Note that with both marking systems, the use of color is optional.

Questions, need more fire safety information or want a professional assessment of your fire extinguishers and other fire prevention systems?  Contact the experts at JB Safety & Rescue Services!