New Haven County Fire Extinguisher Service               

The National Fire Protection Association

(NFPA) has established the requirements for

the number, size, placement, performance,

and maintenance of portable fire

extinguishers. These requirements are

contained in NFPA 10, “Standard for

Portable Fire Extinguishers”. Within this

Standard it is stated that the selection of fire

extinguishers for a given situation is

determined by the character of the fires

anticipated to be encountered, the

construction and occupancy of the property

to be protected, the ambient temperature of

the area where the extinguisher will be

located, and other factors that may dictate

the selection of a particular type of

extinguisher.

CLASSIFICATION

Generally, fire extinguishers are selected

based on the hazard(s) they are intended to

protect. Classifications have been

established to categorize what type of

extinguishing agent is best suited for the fire

hazard. These classifications are A, B, C, D,

and K.

A fire extinguisher assigned a Class A

classification is suitable for use on ordinary

combustibles; wood, paper, cloth, rubber,

and many of the plastics. The B

classification is intended for use on

flammable liquids, combustible liquids,

petroleum greases, oils, oil-based paints,

solvents, alcohols, and flammable gases.

Class C extinguishers are for use on fires

involving energized electrical equipment. For

fires involving combustible metals

(magnesium, lithium, zirconium, etc.), Class

D extinguishers are best to use. An

extinguisher designated Class K best

protects cooking appliances that utilize

cooking media such as vegetable oils and

animal fats.

RATING

Along with the classification, the numerical

rating of an extinguisher is an important

factor in the proper selection of an

extinguisher.

The rating is a measure of the extinguishing

potential of the fire extinguisher and is

developed on the basis of comparative fire

tests (Reference UL 711, Standard for

Rating and Testing of Fire Extinguishers).

Only the Class A and Class B classifications

carry numerical ratings. Basically, the higher

the number associated with the classification

letter, the larger the fire the extinguisher has

the potential to put out. Please refer to

NFPA 10 when determining the rating

necessary for the floor area requiring

protection.

There are no numerical ratings associated

with Class C, D, or K classifications.

Comparative fire tests are not conducted. In

the case of Class C, the electrical

nonconducting characteristics of the agent

are verified, not the extinguishing potential.

For Class D, only the amount of agent and

application method needed to control a

metal fire of a certain size and type is tested.

And for Class K, the fire extinguishing

characteristics of the extinguisher have only

been determined for a single size fire

source. In the typical rating of an

extinguisher, for example 3A-40B:C, the 3

and the 40 indicate the extinguishing

potential of the unit for a Class A and Class

B fire respectively. The C indicates that the

extinguishing agent will not conduct

electricity, preventing shock to the user if

used on energized electrical equipment.

On the following page is a reference chart

with the basic rating parameters for

extinguishers.

SUMMARY

To provide the best protection of life and

property from the destructive force of fire, it

is critical that the proper fire extinguisher

selection be made. The Classification and

Rating of an extinguisher are vital pieces of

information for making that selection.

Using NFPA 10 for guidance, matching the

right fire extinguisher to the potential hazard,

providing a sufficient number of

extinguishers for the area to be protected,

locating the extinguishers for maximum

visibility and accessibility, and personnel

trained in the use and maintenance of the

extinguisher will significantly lessen the risk

of loss.