How many fire extinguishers do I need to install and what size extinguisher should I choose?

People often ask us: how many extinguishers should I install and what size of extinguisher should I choose?

To answer this question, you must first characterize your building. Help yourself by answering the following 3 questions. For large locations, cut out the area to be protected by zones of identical risk.

1- What type of fire is likely to occur?

2- What is the level of risk associated with the area to be protected? (Low, medium or high)

3- What is the area to be protected in relation to its level of risk?

The information written in this article is based on the minimum requirements listed in the N.F.P.A 10 standard. Of course, there is no harm in exceeding these minimum requirements. In fact, many international companies often have higher standards.

The Chemistry of Fire

To generate a fire, we need 3 elements: a combustible material, sufficient heat and an oxidizer. When we think of combustible materials, we usually refer to wood, paper, plastics, flammable liquids, cooking vapours and combustible metals. Sufficient heat can come from a small spark, a flame, an electric arc or other source. For the oxidant it is omnipresent in the air we breathe. The main oxidant is oxygen. As soon as these 3 elements are combined, you have the possibility to generate a fire. To stop combustion, you must dissociate at least one of the elements. This is where the different models of portable fire extinguishers come into action. But you still have to choose the right extinguisher.

Classes of Fire

Fire classes are subject to the fuels involved in combustion. To facilitate their classification, letters are assigned to them. The following is a summary of these letters.

Fires involving fuels such as wood, paper, fabric and certain plastic components are associated with fire class A.

Fires involving flammable liquids as fuel are assigned Fire Class B.

Fires involving live electrical equipment are associated with fire class C.

Fires involving combustible metal particles such as magnesium, aluminum, lithium and others are associated with fire class D.

Fires burning grease or cooking oil vapours as fuel are associated with fire class K.

Levels of risk

Levels of fire risk are often associated with activities carried out in buildings. The level of risk is closely related to the amount of combustible material present. A building or part of a building may be classified as low, medium or high risk.

Low-risk buildings are associated with meeting places, churches, offices, apartments. These places must not contain flammable liquids or the storage of combustible materials.

Medium risk buildings are associated with manufacturing businesses. Where combustible materials are found in greater quantities than in low-risk locations. Often, we find packaged products that are well arranged on the shelves. Flammable liquids are in small quantities and the possibility of D-metal fires is non-existent.

High-risk buildings are often associated with manufacturing operations. In particular, very large quantities of combustible materials are present. This includes areas where combustible is present with high rates of spread. High-risk locations include mechanical garages, parking lots, flour mills, woodworking (sawdust and paints), and areas with type D fire hazards (metal fires). Sometimes it is the manufacturing processes that carry a fire hazard.

The formats on the market dictate the choices.

Obviously, we must use the extinguisher formats available on the market. For example, portable powder extinguishers are only available in 2.5, 5, 10 and 20 lb. sizes. Other types of extinguishers have also had their distinct sizes and specific types of extinguishing agents.

The result described below takes into account the fire extinguisher formats available on the Canadian market. All fire extinguishers sold in Canada must be ULC (Underwriter laboratory of Canada) certified. Manufacturers must submit their extinguisher models for quality testing to determine their extinguishing capability. Depending on the test results, portable fire extinguishers will be assigned a ULC rating. As an example, a 5 lb portable extinguisher will generally have a 3A 10BC rating.

The letters refer to the types of fires.

The letter A refers to the type of fire involving combustible materials such as wood, paper, fabric and the like. This is the basic fire; its expansion may be slow to accelerate. The smaller the size of the fuel, the faster it will spread. Compare the rate of spread between a log of wood versus sawdust.

The letter B corresponds to fires that involve flammable liquids such as gasoline, plastics and other similar products as fuel. These types of fires are very difficult to control and their spread is rapid. It is the equivalent of a barrel of gunpowder.

The letter C corresponds to fires that involve energy equipment. The combustion of the internal components which is composed of wiring and electrical circuits are then under electrical tension. The extinguishing agent must therefore be dielectric (not a current conductor).

The letter D corresponds to fires that involve metals as fuel. Magnesium (Mg) or potassium (K). These 2 metals are the main fuels targeted by portable extinguishers available on the market.

The letter K corresponds to fires generated by cooking oil vapours. This type of hazard is found in commercial kitchens.

The numbers now.

The number corresponds to a unit of extinguishing power obtained in a standardized test. The tests are specific to each class of fire. An exception is class C, where the letter is combined with the letter B, there is no standard firebox. The dielectric properties are decisive for obtaining the class.

An example is the class 3A10BC fire extinguisher commonly called a 5 lb ABC fire extinguisher.

– 3 units of extinguishing power applicable to Type A fire.

– 10 units of extinguishing power applicable to Type B fires.

– The extinguishing agent (ammonium sulfate) is electrically non-conductive.

The following table shows some models of fire extinguishers, weight and ULC rating offered by Sylprotec Inc.

5 LB 10.5 lb 3A10BC
10 LB 19.25 lb 6A80BC
5 CO2 13.5 lb 5BC
10 CO2 28 lb 10BC
K 24.5 1 AK

These weights and ULC dimensions are for example, they may vary depending on the manufacturer.

When the minimum requirements required by N.F.P.A. 10 are carefully linked, the direct relationship between risk and the size of the portable fire extinguisher is understood. High-risk locations require the installation of heavier extinguishers. Conversely, low-risk locations require lighter extinguishers.

In fact, you soon realize that you have to deal with the ratings of the extinguishers that are on the market. If we evaluate that we need to adequately protect a risk with a 2A and 44 B extinguisher. Our solution is to use an existing extinguisher model that meets or exceeds the minimum requirements. In this example, a 10 lb. extinguisher with a rating of 6A 80BC would be appropriate, and then the 2A44BC model is not commercially available.

In order to simplify and bring the solution back with existing formats, here is a summary of the rules I have applied over the years. They allow you to add or to make a complete implementation.

You can install 5 lb ABC dry chemical extinguishers for locations considered low risk (9000 ft2) or medium risk (4500 ft2). 5 lb. extinguishers are not powerful enough to protect high-risk locations.

You can install 10 lb. size ABC dry chemical extinguishers for locations considered low (11,250 sq. ft.) or medium (9,000 sq. ft.) or high (6,000 sq. ft.) risk.

You can install 20 lb. ABC dry chemical extinguishers for locations considered low (11,250 sq. ft.) or medium (9,000 sq. ft.) or high (10,000 sq. ft.) risk.

When you have flammable liquids, then your risk is Type B. You can install 5 lb CO2 fire extinguishers for low-risk locations with a maximum travel distance of 30 ft.

You can call upon Sylprotec to install your portable extinguishers. In addition, Sylprotec offers in-store or via its online shopping site, hooks for all models of portable extinguishers, cabinets to secure portable extinguishers and signs to help you locate them.

The company offers these services in the Greater Montreal area, including Laval and the North Shore of Montreal. The services are subject to travel fees, the prices are listed on their website under the service tab.

Consult htpps:// to learn more about the installation of portable fire extinguishers.

Sylvain Patrice f.p.t.

By the same author:

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Signage in an industrial environment.

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Posters in industrial settings in Canada.