Portable Fire Extinguishers

Question 1

When are portable fire extinguishers primarily used?

Answer 1

For small, incipient fires and early growth fires.

Question 2

How are fire extinguishers classified?

Answer 2

Portable fire extinguishers are classified according to the type of fire that they are designed to extinguish. Often they are suitable to extinguish more than one class of fire while some are only designed for a particular class of fire. Note that they are identified by the class letter or combination of letters for which they’re rated.

Question 3

What are the five classes of fire and fire extinguishers?

Answer 3

Question 4

Which fire extinguishers have letter and numerical ratings?

Answer 4

Class A & B.

For class A, the numerical rating indicates the amount of water (in liters or gallons) that it holds. For class B, it indicates the estimated amount of square feet that it can extinguish.

Question 5

What are the most common combinations of portable fire extinguishers?

Answer 5

• A-B-C (red) - use monoammonium phosphate, a dry chemical with the ability to quickly put out many different types of fires by smothering the flames.
• A-B
• B-C

Question 6

What are the combustibles of class A fires?

Answer 6

Ordinary combustibles, which include fuels such as wood, paper, plastic, rubber, and cloth. Note that these can all be extinguished with water, foam, and dry chemicals.

Question 7

What extinguishes a Class A fire?

Answer 7

Class A fires can be extinguished with water and water-based agents like Class A foam. Dry chemicals will also extinguish fires fueled by Class A materials.

Class A fire extinguishers are also called water cans because they contain water to extinguish the fire. Their sizes range from 1A - 40A where a 1A fire extinguisher has 5 liters of water, 2A has 10, 3A has 3, and so on.

Question 8

How many litres of water would a 30-A fire extinguisher have?

Answer 8

30 x 5 = 150 liters

Question 9

What is the upper limit for class A fire extinguishers in terms of liters?

Answer 9

40 x 5 = 200 liters

Question 10

What are the combustibles of class B fires?

Answer 10

Flammable and combustible liquids and gases such as alcohol, gas, lubricating oils, and propane.

Question 11

What agents are used in class B extinguishers?

Answer 11

Class B fires involve flammable and combustible liquids and gases. Agents used to extinguish these include CO₂, dry chemicals, and Class B foam.

Question 12

How many square feet can a 500-B extinguisher cover when used by a civilian?

Answer 12

500 square feet. The upper limit is 640 square feet.

Question 13

What extinguishes a Class C fire?

Answer 13

Class C fire extinguishers use agents that will not conduct electricity, but it is always best to turn off the power supply before treating the fire, if possible, since it will act as a continuous source of ignition as long as it’s on.

Class C fire extinguishers may contain monoammonium phosphate, potassium bicarbonate, or potassium chloride, all of which are suitable for putting out Class C fires. (Note that water cannot be used on Class C fires since water conducts electricity.) Class C extinguishers use agents that are capable of separating the elements of the fire triangle: fuel, heat, and oxygen. This way, even if the power and ignition sources are still connected, the flames and heat can be suppressed and extinguished, hopefully, long enough for the power source to be disconnected.

If and when the power source is disconnected, and the fire has spread to other areas and fuel sources, the Class C extinguisher can be traded out for a more effective extinguisher (unless you are using an extinguisher that can handle multiple classes).

Question 14

What combustibles are involved in Class D fires?

Answer 14

Combustible metals and alloys such as:

• Lithium
• Titanium
• Magnesium - found in cameras, laptops, luggage, metal box springs for beds, and wheels and transmission components for cars.
• Sodium
• Potassium

Note that you can identify Class D fires by the bright white emissions during the combustion process.

Question 15

Can firefighters use dry chemical extinguishers on combustible metal fires?

Answer 15

No, Class D fires can only be extinguished with Class D extinguishers that use liquid or dry powders.

Question 16

Why can’t water be used to extinguish combustible metal fires?

Answer 16

The water will react violently with the metal and could discharge molten metal.

Question 17

Can firefighters use Class D extinguishers on other types of fires?

Answer 17

No

Question 18

What is a Class K fire?

Answer 18

Class K fires involve combustible cooking oils such as vegetable oils or animal fats that burn at extremely high temperatures (a.k.a. kitchen fires).

Question 19

What is saponification?

Answer 19

Class K fire extinguishers work because of saponification - a process of converting fatty acids or fats in cooking oils to a saopy film.

Question 20

What extinguishes a Class K fire?

Answer 20

Class K fire extinguishers use extinguishing agents that separate and absorb the heat elements of the fire—the fuel, heat, and oxygen necessary to start a fire. Wet mist containing chemicals such as potassium carbonate, potassium acetate, or potassium citrate that mix with the cooking grease create a blanket that cools the flammable liquid to block oxygen, extinguishing the flames and preventing reignition.

Class K fires can only be extinguished with Class K extinguishers, and should never be sprayed with water as this can increase the spread of the cooking liquids.

Question 21

What are the four ways in which extinguishers act upon the combustibles?

Answer 21

In addition to being rated based on the type of fire that they extinguish, fire extinguishers are also rated according to the type of extinguishing agent and mechanism used to expel the contents. These are:

• Smothering - extinguish fire by excluding oxygen from the burning process
  
  • carbon dioxide
  • foam
  • wet chemical
  • dry powder
• Cooling - reduce the burning material below its ignition temperature
  
  • water
• Chemical flame inhibition - interrupts the chemical chain reaction in the burning process
  
  • clean agent
  • dry chemical
• Saponification - converts fatty acids in vegetable oils and animal fats to a soapy film
  
  • wet chemical

Question 22

What are the three methods of extinguisher expelation?

Answer 22

• Manual pump
• Stored Pressure
• Pressure cartridge

Question 23

In what two ways do AFFF extinguishers differ from stored-pressure water extinguishers?

Answer 23

1. AFFF has a specified amount of AFFF concentrate mixed with water to form a foam mixture
2. AFFF has an air-aspirating foam nozzle, which creates better quality foam

Question 24

True or false: you can use an AFFF extinguisher for flowing fuels.

Answer 24

False. You can only use them for stagnant fuels.

Question 25

What are halotron extinguishers?

Answer 25

They are used in expensive electrical circuits like airplane cockpits and computer fires. They smother the fire without damaging the technology and the ozone layer.

Question 26

When are CO₂ extinguishers used?

Answer 26

They are used for Class B and Class C fires.

Question 27

What is the difference between a dry chemical extinguisher and a dry powder extinguisher?

Answer 27

Dry chemical extinguishers are used for Class A, B, and C fires, while dry powder are used for Class D fires.

Question 28

When many extinguisher options are available, how do you decide which is the best?

Answer 28

We want to minimize damage to life and property, while still being able to extinguish the fire. We must concider:

• Classification of the burning fuel
• Hazards to protect against
• Atmospheric conditions
• Ease of handling
• Rating of extinguisher
• Size and intesity of fire
• Availability of trained personel
• Any hazards to life or operational concerns

Question 29

What is the PASS application method?

Answer 29

1. Pull - the pin, breaking the thin wire or plastic seal
2. Aim - the nozzle at the base of the fire
3. Squeeze - the handles together to release a short burst to test the extinguisher, then squeeze continuously to release the agent
4. Sweep - the nozzle back and forth to cover the burning material

Question 30

What four things should be inspected on a fire extinguisher before use?

Answer 30

External condition
Hose/nozzle
weight
pressure gauge