Today, we’re going to talk about fire extinguishers. Fire extinguishers are necessities in the workplace, in the home, on construction sites, and even in vehicles. During this session, we’ll discuss what causes fires and how fire extinguishers put out fires. You’ll learn about different classes of fires and the types of extinguisher to use on each class of fire. You’ll also learn how to use a fire extinguisher correctly, and you’ll learn about different fire suppressant materials.

Session Objectives

The main objective of this session is to make sure that you know how to use a fire extinguisher correctly and know how to select the right extinguisher for different kinds of fires. By the time the session is over, you should be able to:

• Identify different classes of fire;
• Choose the appropriate type of extinguisher;
• Use a fire extinguisher correctly; and
• Inspect and maintain extinguishers properly.

Pre-quiz: How Much Do You Know?

Before we begin the session, let’s take a few minutes to see how much you already know about fire extinguishers. Decide which of the statements on the screen are true or false.

• The same kind of fire extinguisher will put out any type of fire.
• You should not try to fight a large, spreading fire with an extinguisher.
• To get started and keep burning, a fire needs only two things—fuel and an ignition source.
• When using an extinguisher, you should aim the nozzle at the top of the fire.

How did you do? Did you get all the answers right?

If not, don’t worry. You’ll learn all about these issues and a lot more during the session.

How Fires Start and Keep Burning

Fire is the result of a chemical combustion reaction. Four things are necessary for a fire to get started and for the chemical reaction to continue—oxygen, fuel, heat, and an uninhibited chain reaction.

• Here’s how fire works. There’s plenty of oxygen in the air to support fire. So that’s the first element required for a fire to get started.
• Next, some sort of fuel is required, such as wood, paper, or gasoline. But wood, paper, gasoline, or other fuels don’t spontaneously catch fire just because they are surrounded by oxygen. For the chemical combustion reaction to take place, the fuel has to be heated to its ignition temperature by some (*) outside source. The source of ignition might be a burning cigarette, a spark, overheated equipment, static electricity, or a chemical reaction.
• Once ignited, the heat of the flame keeps the fuel at the ignition temperature, so it will continue to burn as long as there are fuel and oxygen.
• This combination of heat, oxygen, and fuel working together creates a chemical chain reaction called combustion.

Think about the possible sources of ignition in your work area.

Class A Fires

Now let’s move on to the different classes of fires. Fires are generally classified according to the type of fuel involved. Class A fires, for example, involve ordinary combustible materials such as:

• Wood, pallets, and lumber;
• Paper and cardboard;
• Cloth;
• Plastic and foam; and
• Garbage.

Think about your work area. Can you identify all the different kinds of ordinary combustibles in the area where you work?

Class B Fires

Class B fires involve flammable liquids such as:

• Gasoline, kerosene, and other liquid fuels;
• Oil and other combustible liquids;
• Common solvents such as paint thinners, mineral spirits, and organic solvents found in laboratories; and
• Grease that is often found in kitchens.

Are there any flammable liquids in your work area?

Class C Fires

Class C fires involve energized electrical equipment such as:

• Appliances, including stoves, washing machines, and dryers;
• Switches, outlets, power cords, and extension cords;
• Panel boxes and circuit breakers; and
• Power tools, including drills, sanders, grinders, and saws.

Are you aware of all the types of energized electrical equipment in your work area?

Class D Fires

Class D fires involve combustible metals. For example:

• Magnesium metals, chips, or grinding dusts, which can be found in some metal shops.
• Titanium metals, chips, or grinding dusts, which can be found in many aerospace sheet metal facilities.
• Potassium and sodium, which in their pure elemental forms are soft, ductile, malleable metals that can be easily cut with a knife or drawn into wire. These metals react with air and water, and are usually stored in a material such as mineral oil. Because they react with water, extinguishing a potassium or sodium fire with water could result in an explosion.
• Pyrophoric materials are also combustible metals. They are highly reactive substances used in the synthesis of organic chemicals. Special training is required to store and handle these materials safely. Examples include alkyllithiums, alkylmagnesiums, and diphosphine. A Class D fire extinguisher must be on hand when handling these materials. Using the wrong extinguisher could result in a larger fire.

If you work with combustible metals or in a work area where these metals are stored or handled, make sure there are Class D extinguishers available.

Class K Fires

The last class of fire is Class K fires, which are kitchen fires. This class of fire involves:

• Cooking oil, and
• Fat.

These fires generally occur in kitchens at restaurants and other establishments where deep fat fryers are used. Wet chemical fire extinguishers, which contain a potassium acetate–based, low pH agent are approved for Class K fires.

Exercise

Now, it’s time for an exercise. See if you remember how we’ve defined the different classes of fire by matching the class of fire in the column on the left to the material in the column on the right that fuels the fire.

How did you do? Did you correctly match the class of fire to the material? Are you setting goals to help yourself remember the information after you complete the course?

Review

Now it’s time to ask yourself if you understand the information presented so far? Do you understand what we’ve said about:

• How fires get started and keep burning?
• Different classes of fires?

It’s important to understand this information so that you can use fire extinguishers correctly and safely to extinguish different kinds of fires.

Let’s continue now to the next slide and talk about extinguishing fires.

Extinguishing Fires

Fire extinguishers are designed to remove at least one of the three elements of fire so that the fire will die out. In other words, to extinguish a fire, you must remove either:

• Heat,
• Oxygen, or
• Fuel.

The best way to remove heat from an ordinary fire is to dump water on the fire. This cools the fuel to below the ignition point, which interrupts the combustion cycle.

To remove oxygen, you can smother a fire so that it is not exposed to air. One way to smother a fire is to cover it with a heavy blanket. Another way is to dump nonflammable material on it, such as sand, baking soda, or inert gases.

Removing fuel is the most difficult way to extinguish a fire because fuels are usually everywhere. In most cases, the fuel will only be removed once the fire burns it all up.

Water Extinguishers

• Water extinguishers contain water and compressed gas. They spray a stream of water on the fire. Water extinguishers are rated only for Class A fires—that is, fires caused by ordinary combustibles such as wood, paper, cardboard, plastic, and garbage.
• You should not use water extinguishers on Class B fires. Class B fires involve flammable liquids such as oil, gasoline, solvents, and grease. All of these fuels float on water, so they will continue to burn and actually spread out if you try to extinguish them with water. Furthermore, a hot grease fire hit by a spray of cold water will result in the splattering of burning grease, which could spread the fire and injure the person using the extinguisher.
• Spraying water on a Class C fire that involves electrical equipment could result in an electrical shock.
• The extremely hot temperature of a Class D fire involving combustible metals will break the water molecules down into hydrogen and oxygen molecules that will actually feed, rather than extinguish, the fire.

Remember that all five extinguishers use a significant amount of pressure when activated. Be careful not to point the stream toward anyone.

Do you know where water extinguishers are located in your work area?

Dry Chemical Extinguishers

• Dry chemical extinguishers are your best all-around choice for the average industrial, manufacturing, office, or warehouse environment. They have the advantage of leaving a blanket of nonflammable powder on the extinguished material, which reduces the likelihood of reignition.
• Class BC-rated dry chemical extinguishers contain either sodium bicarbonate, which is normal baking soda, or potassium bicarbonate, which is nearly identical to baking soda, as the extinguishing agent. The propellant, which makes the powder spray out of the extinguisher, is an inert compressed gas.
• Class ABC-rated dry chemical extinguishers are the most common. They contain ammonium phosphate as the extinguishing agent and an inert compressed gas as the propellant.

Remember that any fire extinguisher can contain materials that displace oxygen—thus, making it more difficult to breathe. Once an extinguisher has been used, the area should be cleared and ventilated.

Do you know where to locate dry chemical fire extinguishers in your work area?

Carbon Dioxide (CO₂) Extinguishers

Carbon dioxide, or CO₂ extinguishers put out fires by displacing the oxygen near the fire, which smothers the fire. The carbon dioxide escaping from the extinguisher also cools the surrounding air as it expands, which helps cool down the burning material.

• CO₂ extinguishers are primarily effective on Class B fires, which you’ll remember involve flammable liquids, and Class C fires, which are electrical fires. CO₂ is not effective on Class A fires and should never be used on Class D fires.
• The advantage of CO₂ extinguishers is that they do not leave any residue. Because of that, they are a good choice for fires involving computers and other electronics.
• The disadvantage of CO₂ extinguishers is that the gas disperses quickly, so they are only effective at relatively close range—a distance of 3 to 8 feet from the fire.

Do you know where to locate CO2 fire extinguishers in your work area?

Metal/Sand Extinguishers

• Another type of fire extinguisher is the metal/sand extinguisher. These extinguishers are approved for Class D fires involving combustible metals only.
• Powdered copper is preferred for fires that involve lithium and lithium alloys. It will cling to a vertical surface, making it the preferred agent for three-dimensional and flowing Class D fires.
• Sodium chloride works well for metal fires involving magnesium, sodium, potassium, sodium potassium alloys, uranium, and powdered aluminum.
• Metal/sand extinguishers work when the extreme heat from the fire causes the extinguishing agent to cake and form a crust over the fire that excludes air and dissipates heat.

Anyone who works with combustible metals should know where to locate an approved Class D extinguisher.

Halon Extinguishers

Halon extinguishers provide another tool for fighting fires. Halon extinguishers contain a gas that interrupts the chemical reaction that takes place when fuel burns.

• Halon extinguishers are only effective on Class B and Class C fires.
• The advantage of Halon extinguishers is that they leave no residue to clean up. That’s why they are often used on fires involving valuable electrical equipment.
• The disadvantage of Halon extinguishers is that they dissipate quickly and have a limited range of only 4 to 6 feet.
• Halon 1211 production was banned by international agreement in 1994. However, recycled Halon is still available for recharging these extinguishers. Halon extinguishers are expensive to maintain because servicing companies must use a closed system that prevents the escape of Halon during maintenance.

Do you remember what kinds of ignition sources are involved in Class B and C fires, the only ones Halon extinguishers can be used on effectively?

Halotron I Extinguishers

• Halotron I is an ozone-friendly replacement for Halon extinguishers.
• Halotron I discharges a liquid with high visibility, but does not leave any residue. It is also nonconducting, which makes Halotron I extinguishers ideal for computer rooms, clean rooms, telecommunications equipment, and other electronics.
• Halotron I is rated for both Class B and C fires.

If you work with or around electronics, you may be familiar with Halotron I extinguishers.

FE-36 Extinguishers

• FE-36 is a DuPont-manufactured Halon 1211 and Halotron I replacement.
• It’s less toxic that the other two but retains the same extinguishing properties.
• It also has zero ozone-depleting potential and is not scheduled to be phased out of production.
• FE-36 extinguishers are rated for Class B and C fires, and are especially useful for fires that involve expensive computer and electronics equipment.

If you work with computer or other electronics equipment, you may be familiar with FE-36 extinguishers.

Water Mist Extinguishers

The last type of extinguisher we’re going to talk about today is the water mist extinguisher. Although water mist extinguishers use water as the extinguishing agent, they are somewhat different from normal water extinguishers that should only be used on Class A fires.

• Water mist extinguishers are generally used for Class A fires where a potential Class C hazard exists. You’ll remember that Class C fires involve electricity and Class A fires involve ordinary combustibles like paper, cardboard, and trash.
• The misting nozzle on this type of extinguisher provides safety from potential electrical shock.
• It also reduces the scattering of burning materials that can occur with an ordinary water extinguisher.
• Water mist extinguishers are a good choice for hospital environments, areas that contain books and documents, and clean rooms. A nonmagnetic version of the water mist extinguisher is preferred for MRI and nuclear magnetic resonance spectrometer facilities.

If you work in such an environment, you may be familiar with water mist extinguishers.

Fight-or-Flight Decision

When a fire occurs, you have to make a fight-or-flight decision: Will you evacuate or stay and fight the fire with an extinguisher? Only attempt to use an extinguisher if you can say “yes” to every point on this slide and the next slide. If these conditions have not been met, do not fight the fire yourself—evacuate the area.

Here are the conditions under which you may safely use an extinguisher:

• The fire alarm has been activated, which means other employees are notified of the fire and are evacuating the building or coming to your aid.
• The fire department has been called. Someone has called 911 and is on the line with the dispatcher.
• The fire is small, contained, and not spreading beyond its starting point.
• The smoke is not bad. You can easily stay low and avoid the smoke while using the fire extinguisher.

Fight-or-Flight Decision (cont.)

Here are a few more conditions in which you may safely use an extinguisher:

• The nearest exit is clear so that you can easily evacuate if the fire suddenly increases in size. When fighting a fire with an extinguisher, your back should always be toward the exit so that you know you can always escape.
• The correct extinguisher for the class of fire is nearby.
• And finally, you have been trained to use a fire extinguisher correctly.

Think about these requirements for safely fighting a fire with an extinguisher. Also think about the procedures you’ve been taught for safely evacuating the building in case it is not safe to fight a fire with an extinguisher.

How to Use a Fire Extinguisher Effectively

Even though fire extinguishers come in a number of shapes and sizes, they all operate in a similar manner. To use an extinguisher effectively, remember the PASS system. PASS stands for Pull, Aim, Squeeze, and Sweep.

Here’s how it works.

• Pull the pin at the top of the extinguisher. The pin keeps the handle from being accidentally pressed when the extinguisher is not in use.
• Aim the nozzle toward the base of the fire. Stand 8 to 10 feet from the fire. Note that some types of extinguishers require you to be closer.
• Squeeze the handle lever to discharge the extinguisher. When you release the handle lever, the discharge will stop. Keeping the lever squeezed will result in a continuous flow of extinguishing agent. Squeezing and releasing the lever will result in short bursts of extinguishing agent.
• Sweep the nozzle back and forth toward the base of the fire as you squeeze the handle lever. After the fire appears to be out, watch it carefully, since it might reignite.

Think about the steps in the PASS system so you can use it effectively.

Extinguisher Inspections

Fire extinguishers in the workplace must be visually inspected at least once a month, and more often in severe work environments. When inspecting an extinguisher, make sure that access to the extinguisher is not blocked by equipment, stock, or scrap. Coats, air hoses, or electrical cords must not be hanging on an extinguisher, either.

• The pressure of the extinguisher must be at the recommended level. On extinguishers equipped with a gauge, the needle should be in the green zone. This means the pressure is not too high or too low. Report and replace an extinguisher if the pressure is not at the recommended level.
• The pin and the tamperproof seal must be intact. As we said in the previous slide, the pin prevents accidental discharge. The seal shows that the pin has not been removed and that the extinguisher is ready to use in an emergency. Report and replace the extinguisher if the pin or seal are missing.
• Finally, be sure that the extinguisher doesn’t have any dents, rust, chemical damage, or any other signs of abuse or wear.

If you’re responsible for inspecting extinguishers, make sure you use your facility’s inspection checklist and follow inspection procedures.

Extinguisher Care and Maintenance

To make sure extinguishers are in good operating condition when you need them, they must be properly cared for and maintained.

• Extinguishers should be kept clean. Wipe off any corrosive deposits, oil, or grease that may land on them.
• Any damaged, dented, or leaking extinguishers must be replaced. So must extinguishers with missing pins or seals, or those where the pressure is not correct.
• When an extinguisher is discharged, do not put it back in place. Turn it in to maintenance so that it can be recharged. OSHA requires us to supply a replacement extinguisher while one is being recharged or serviced.
• Extinguishers must undergo hydrostatic testing, or pressure testing every 5 or 12 years depending on the type of extinguisher
• Public safety rules in many states require that non-rechargeable extinguishers be removed from service at 12 years intervals- there is no OSHA requirement for removal from service of non-rechargeable extinguishers.

Location and Signs

Extinguishers must be readily accessible and clearly marked. They cannot be blocked by equipment or materials, as we’ve said, and they must be mounted so that they can be easily removed in an emergency. The location of extinguishers must be identified with highly visible signs that point toward the extinguisher and can be seen from all over the work area.

• Class A extinguishers cannot be located more than 75 feet from any point in the workplace where ordinary combustibles might be involved in a fire. This measurement includes walking down aisles, around equipment, or around materials that might be in the way.
• Class B extinguishers must be located within 50 feet of areas where flammable liquids might be involved in a fire.
• Class C extinguishers, used for electrical fires, must be distributed in the same pattern as Class A and Class B extinguishers, which is 50 to 75 feet from the point of use.
• Travel distance between Class D extinguishers and work areas with combustible metals must be no more than 75 feet.
• Class K extinguishers must be located no more than 30 feet away in locations where potential fire hazards from vegetable or animal oils and fats exist.

Do you remember the PASS system?

Now it’s time for an exercise. As we said earlier, the PASS system is an easy way to remember how to use a fire extinguisher effectively. See if you can remember what PASS stands for.

If you didn’t remember this, you might want to go back and review.

Review

Now it’s time to ask yourself if you understand the information presented in the previous slides about how to use and maintain fire extinguishers?

Do you understand:

• How fires are extinguished?
• How to choose the right extinguisher for different classes of fires?
• Fight-or-flight considerations?
• How to use a fire extinguisher effectively?
• How to visually inspect an extinguisher?
• Care and maintenance of extinguishers?
• Location and signage requirements under the OSHA standard?

It’s important to understand this information so that you can choose the right fire extinguisher, use it effectively, and make sure extinguishers are in good condition and ready to use in an emergency.

Let’s continue now to the last slide and some key points to remember.

Key Points to Remember

Here are the main points to remember about this session on fire extinguishers:

• Understand how fires start, and be able to identify different kinds of fire hazards in the workplace.
• Make sure you know the proper type of extinguisher to use for different classes of fire and the location of those extinguishers.
• Learn how to use an extinguisher effectively and how to inspect extinguishers to be sure they are in good condition.
• Only fight small, contained fires with an extinguisher, and be prepared to evacuate if the fire spreads.

This concludes the Fire Extinguishers training session. Will you remember this information after the course is complete, or do you need to go back and review?