fast facts 

Portable Fire Extinguishers Are Often the 

First Line of Defense for Fire Suppression 

November 2009 

Office of Compliance 

advancing safety, health, and workplace rights in the legislative branch 

www.compliance.gov 

A portable fire extinguisher is often the first line of defense against a small fire. A trained person can save lives and property by using an extinguisher to put out or control a small fire until the fire department arrives. However, if the fire is too

large and/or intense to use a portable fire extinguisher, you should promptly evacuate the building. As you evacuate, you 

should activate the closest fire alarm pull station, provided you are not putting yourself at risk. 

Types of Fire Extinguishers and Classification of Fires

There are several types of fire extinguishers that are suited for different classes of fires. Carbon dioxide, dry chemical, and

wet chemical agent fire extinguishers are some of the many that are used. Halogenated fire extinguisher agents are being 

phased out because these agents break down the earth’s ozone barrier and are considered an environmental hazard. The 

following table shows which type of fire extinguisher should be used for each class of fire. 

Type of Fire and Extinguishing 

 Agent Characteristics

Dry 

Chemical 

Extinguisher

Wet 

Chemical 

Extinguisher

Carbon 

Dioxide 

Extinguisher

 Pressurized 

 Water 

 Extinguisher

Class A fires involve ordinary combustible materials such 

as wood, cloth, paper, and plastics. Class A Extinguishers 

use agents that cool down the fuel below its ignition temperature or interfere with the combustion chemical process 

or isolate or dilute vapors from ignition sources. 

 

 YES 

 

 YES 

 

 NO 

 

 YES 

Class B fires involve flammable and combustible liquids, 

flammable gases, oils, oil-based paints, solvents, and alcohol. Class B Extinguishers use agents that interfere with 

the combustion chemical process or isolate or dilute vapors from ignition sources. 

 

 YES 

 

 NO 

 

 YES 

 

 NO 

Class C fires involve energized electrical equipment, 

such as overheating electrical wires. Class C Extinguishers 

use agents that are non-conductors of electricity and interfere with combustion chemical process or isolate or dilute 

vapors from ignition sources. 

 

 YES 

 

 NO 

 

 YES 

 

 NO 

Class D fires involve combustible metals such as magnesium, titanium, sodium, lithium, and potassium. Class D 

Extinguishers use agents that do not provide any additional oxygen and that interfere with or isolate the vapors 

or fumes from ignition sources. 

 

 NO 

 

 NO 

 

 NO 

 

 NO 

Class K fires involve cooking appliances or combustible 

cooking media such as vegetable or animal oils and fats. 

Class K Extinguishers use agents that cool and interfere 

with the combustion chemical process or isolate or dilute 

vapors from ignition sources. 

 

 NO 

 

 YES 

 

 YES 

 

 NO 
Considerations concerning extinguishing Class B and D fires

Unless there is reasonable assurance that the source of fuel feeding the fire can be completely shut off, do not 

attempt to extinguish Class B fires because a potential to create a vapor or gas-air explosion hazard can occur. 

For Class D fires, due to extreme temperatures of the chemical reactions between burning metals and water 

and other extinguishing agents, dry powder agents are considered to be the most effective extinguishing 

agents. The application of various types of dry powder agents will depend on the type of combustible metal 

burning. For example, Met-L-X powder is suitable for magnesium, potassium, and sodium-potassium alloy 

metal fires, and Na-X powder is suitable for sodium metal fires. 

Accessibility and Obstruction

Easy accessibility and visibility of extinguishers are essential 

because fires spread and grow at a rapid rate. Furthermore, an 

adequate number of fire extinguishers must be placed throughout the 

building. Class A fire extinguishers 

are expected to be placed so that one 

is available within 75 feet; within 50 

feet from the hazard area for Class B 

extinguishers. Class C is based on 

the placement of fire extinguishers 

for Class A or B. The fire extinguisher in Figure 1 is properly hung 

on the wall but is obscured from 

view, not easily accessible, and its 

location is not marked properly. The carbon dioxide extinguishers (CO2) shown 

in Figure 2 are not properly secured and placed. Because CO2 extinguishers are 

compressed gas cylinders, they must be properly secured by means of a steel 

bracket or other approved method. In addition, use of CO2 extinguishers must be 

limited to open spaces due to the fact that the gas may displace the oxygen in the 

air, creating a hazardous area for persons within confined spaces. 

Proper Training 

Any person using fire extinguishers in the event of fire must be properly trained per OSHA regulations so that 

they can evaluate the situation and respond in a timely manner without putting themselves and others at risk. 

Using a fire extinguisher may seem relatively simple; however, trained responders must assess the type and 

magnitude of the fire. In some cases, even a trained person may not be able to successfully extinguish a fire. 

Improper fire extinguisher selection may even cause the fire to spread more rapidly. Therefore, untrained persons should never attempt to use fire extinguishers. 

 Figure 1 Fire extinguisher 

 obstructed from view and 

 not easily accessible. 

Figure 2 Carbon dioxide extinguisher not properly 

secured and placed. 
fast stats 

 

 

 

This information does not constitute advice or an official ruling of the Office of Compliance or the Board 

of Directors and is intended for educational purposes only. For further information, please refer to the 

Congressional Accountability Act (2 U.S.C. 1301 et seq.) and the regulations issued by the Board, or you 

may contact the Office of Compliance.

The Office of Compliance advances safety, 

health, and workplace rights in the U.S. 

Congress and the Legislative Branch. Established as an independent agency by the 

Congressional Accountability Act of 1995, 

the Office educates employees and employing offices about their rights and responsibilities under the Act, provides an impartial 

dispute resolution process, and investigates 

and remedies violations of the Act. 

If you have any questions, please do not 

hesitate to contact the Office of Compliance: 

Room LA 200, John Adams Building 

110 Second Street, SE 

Washington, D.C. 20540 

t/ 202-724-9250 

tdd/ 202-426-1912 

Peter Ames Eveleth f/ 202-426-1913 

General Counsel 

Mary-Margaret Smith 

Editor Download the entire Fast Facts suite at http://www.compliance.gov 

Inspection and Maintenance 

Fire extinguishers, like all other fire protection systems, need monthly periodic inspections (NFPA 10 Section 

7.2.1.2) and annual maintenance (NFPA 10 Section 7.3.1.1.1) to ensure that they are in serviceable condition. The 

monthly periodic inspection checklist must consist of at least the following items: 1) location in designated space; 2) 

no obstructions to access or visibility; 3) pressure gauge in the operable range; and 4) no obvious physical damage 

or conditions such as leakage or corrosion to prevent its operation. In addition, a dry chemical extinguisher with a 

gauge indicating a low pressure level must be serviced before it can be used again. 

Smaller sized portable fire extinguishers can be completely discharged in 15 seconds or less; therefore operator training and 

conspicuous placement of accessible extinguishers is most important for effective use. Portable fire extinguishers are often 

considered to be the first line of defense for fire suppression. 

Regulation Requirements

• Fire extinguishers must be maintained in a fully charged and operable condition and shall be kept in their designated places 

at all times when they are not being used. (NFPA 10 Section 6.1.2 and OSHA 29 CFR§ 1910.157(c)(4)) 

• Fire extinguishers must be located along normal paths of travel, including exits from areas. (NFPA 10 Section 6.1.3.2) 

• Fire extinguishers must be conspicuously located where they are readily accessible and available immediately in the event of 

fire. (NFPA 10 Section 6.1.3.1 and OSHA 29 CFR§ 1910.157(c)(1)) 

• OSHA requires that employers “provide an educational program to familiarize employees with the general principles of fire 

extinguisher use and the hazards involved with incipient stage fire fighting. (29 CFR§ 1910.157(g)(1)) 

• OSHA requires employers to provide this educational program to those employees who may use fire extinguishers to put out 

fires “upon initial employment and at least annually thereafter.” (29 CFR§ 1910.157(g)(2)) 

Considerations concerning Class K fires 

Class K fires are cooking oil fires. Tests have shown that wet chemical extinguishers are several times more effective 

than dry chemical agents at extinguishing Class K fires. Class K fire extinguishers must have a placard conspicuously 

placed near it that states that an existing automatic fire suppression system protecting this area must be activated prior 

to using the fire extinguisher per National Fire Protection Association, NFPA 10.