Fire Extinguisher Ratings and Commercial Buildings: What You Need to Know

Key Takeaways

• Fire extinguisher ratings are a way to classify their effectiveness against certain types of fires. They are denoted by letters and numbers that indicate the type and size of fire they can put out.
• Commercial buildings are evaluated and assigned a fire hazard level based on the business scope and what the building contains. The fire hazard level determines the right type and number of fire extinguishers required for a given building.
• Fire extinguisher placement is also important to ensure accessibility and visibility in the event of a fire. NFPA 10 provides guidelines for the maximum travel distance and floor area per extinguisher, as well as the mounting height and location of extinguishers.

What are Fire Extinguisher Ratings?

Fire extinguisher ratings are a way to classify their effectiveness against certain types of fires. You’ll see them as a letter followed by a number outlining which fire can be extinguished. The letters denote the type of combustible material that the extinguisher can put out effectively. The numbers indicate the relative extinguishing potential, with higher numbers meaning more fire-fighting power. The following table summarizes the common fire extinguisher ratings and their meanings:

Rating	Fire Class	Description
A	Ordinary combustibles	Fires in materials such as wood, paper, cloth, rubber, and plastics
B	Flammable liquids	Fires in liquids such as gasoline, oil, paint, solvents, and alcohols
C	Energized electrical equipment	Fires involving live wires, appliances, computers, and other electrical devices
D	Combustible metals	Fires in metals such as magnesium, titanium, sodium, and potassium
K	Cooking media	Fires in cooking oils, fats, greases, and animal products

Some fire extinguishers may have multiple ratings, such as ABC or BC, which means they can be used on more than one type of fire. However, not all fire extinguishers are suitable for all types of fires. For example, using a water-based extinguisher on an electrical fire can cause electrocution or shock. Using a dry chemical extinguisher on a metal fire can cause a violent reaction or explosion. Therefore, it is important to choose the right fire extinguisher for the right fire.

How to Choose the Right Fire Extinguisher for Your Commercial Building?

Commercial buildings are evaluated and assigned a fire hazard level based on the business scope and what the building contains. The fire hazard level determines the right type and number of fire extinguishers required for a given building. The following table shows the three fire hazard levels and their corresponding examples:

Fire Hazard Level	Examples
Light	Offices, classrooms, churches, assembly halls
Ordinary	Mercantile occupancies, light manufacturing, warehouses
Extra	Woodworking, flammable liquids storage, spray painting

The type of fire extinguisher needed for each fire hazard level depends on the type of fire that may occur in that building. For example, a light hazard occupancy may only need Class A extinguishers for ordinary combustibles. An ordinary hazard occupancy may need Class A and B extinguishers for flammable liquids and gases. An extra hazard occupancy may need Class A, B, C, D, or K extinguishers depending on the specific materials involved.

The number of fire extinguishers needed for each fire hazard level depends on two factors: the maximum travel distance and the maximum floor area per extinguisher. The maximum travel distance is the actual distance that a person would need to walk to reach an extinguisher from any point in the building. The maximum floor area per extinguisher is the total area that one extinguisher can cover effectively. Both factors vary depending on the rating and size of the extinguisher. The following table shows some examples of the maximum travel distance and floor area per extinguisher for different ratings:

Rating	Maximum Travel Distance (ft)	Maximum Floor Area per Extinguisher (ft2)
2-A	75	3,000
4-A	75	6,000
10-A	75	15,000
20-A	75	30,000
40-A	75	60,000
5-B	30	N/A
10-B	50	N/A
20-B	50	N/A
40-B	50	N/A
80-B	50	N/A

To determine the number of fire extinguishers needed for a commercial building, one must follow the most restrictive of the two factors. For example, if a building has a 10-A rated extinguisher, the maximum travel distance is 75 ft and the maximum floor area per extinguisher is 15,000 ft2. If the building has a floor area of 20,000 ft2, then two extinguishers are needed to cover the entire area. If the building has a floor area of 10,000 ft2, but the shape is such that some points are more than 75 ft away from the extinguisher, then two extinguishers are also needed to reduce the travel distance.

How to Place Fire Extinguishers in Your Commercial Building?

Fire extinguisher placement is also important to ensure accessibility and visibility in the event of a fire. NFPA 10 provides guidelines for the mounting height and location of extinguishers. The following are some general rules for fire extinguisher placement:

• Fire extinguishers should be mounted on walls or on approved stands or cabinets.
• Fire extinguishers should be located along normal paths of travel and near exits and stairways.
• Fire extinguishers should be placed near the potential sources of fire, such as electrical panels, heating equipment, cooking appliances, etc.
• Fire extinguishers should be clearly visible and identifiable by signs or labels.
• Fire extinguishers should be mounted at a height that is easy to reach for most people. The top of the extinguisher should not be more than 5 ft above the floor for those weighing less than 40 lbs, and not more than 3.5 ft above the floor for those weighing more than 40 lbs.

Conclusion

Fire extinguisher ratings and commercial buildings are closely related. By understanding the meaning and importance of fire extinguisher ratings, you can choose the right type and number of fire extinguishers for your commercial building. By following the guidelines for fire extinguisher placement, you can ensure the safety and protection of your property and occupants in case of a fire.