Guide to Fire Extinguisher Placement per NFPA 10

Fire Classes and Extinguisher Types

Fires are classified by the fuel involved, and extinguishers are rated to match. Using the wrong extinguisher type can be ineffective or dangerous. A water extinguisher on a grease fire spreads the burning oil, and a CO2 extinguisher on a Class D metal fire can cause a violent reaction.

Class A: Ordinary combustibles: wood, paper, cloth, rubber, plastics. Extinguishing agents: water, foam, dry chemical (ABC), wet chemical. These are the most common fires and the baseline for travel distance requirements.

Class B: Flammable liquids and gases: gasoline, oil, grease, solvents, propane. Agents: CO2, dry chemical (BC or ABC), foam, clean agents (Halotron, FE-36). Never use water on Class B fires; it can spread the burning liquid.

Class C: Energized electrical equipment. Agents: CO2, dry chemical, clean agents. Once power is disconnected, the fire becomes Class A or B depending on what is burning. Water and foam are conductive and must not be used on energized equipment.

Class D: Combustible metals: magnesium, titanium, sodium, lithium, zirconium. Agents: specialized dry powder agents (Met-L-X, Lith-X, copper powder). Standard ABC extinguishers do not work on metal fires and can worsen the situation.

Class K: Cooking oils and fats in commercial kitchens. Agents: wet chemical (potassium acetate solution) that forms a foam blanket over the burning oil. Required in all commercial cooking operations with deep fryers, griddles, or grills.

Travel Distance Requirements

Travel distance is the maximum distance a person should have to walk from any point in the building to reach the nearest appropriate extinguisher. NFPA 10 specifies these distances based on fire class and hazard severity.

Class A hazards: Maximum travel distance is 75 feet to the nearest Class A extinguisher. This means extinguishers must be spaced no more than 150 feet apart along normal paths of travel (75 feet from each end). In practice, place extinguishers at exits, stairways, and along corridors so no occupied area is more than 75 feet from one.

Class B hazards: Maximum travel distance is 50 feet. The extinguisher must also be sized to match the hazard. A 10-B:C extinguisher covers a different area than a 40-B:C. For areas with large quantities of flammable liquids, multiple extinguishers or larger units may be required to provide adequate protection within the 50-foot travel distance.

Class K hazards: Maximum travel distance is 30 feet from commercial cooking equipment. The extinguisher must be a wet chemical type specifically rated for Class K fires. Most commercial kitchen hoods also require a fixed suppression system, but the portable extinguisher is still required as backup.

Class D hazards: Maximum travel distance is 75 feet, but the extinguisher must contain the correct agent for the specific metal being processed. Class D extinguishers are not interchangeable. A sodium-rated agent may not work on magnesium.

Mounting Height, Visibility, and Signage

NFPA 10 specifies mounting heights based on extinguisher weight. Extinguishers weighing 40 pounds or less must be mounted so the top of the extinguisher is no more than 5 feet above the floor. Extinguishers weighing more than 40 pounds must be mounted with the top no more than 3.5 feet above the floor. In all cases, the bottom of the extinguisher must be at least 4 inches above the floor to prevent tripping hazards and allow cleaning underneath.

Signage: Extinguisher locations must be clearly marked with signs visible from the normal approach direction. In large open areas, overhead signs or directional arrows help workers find extinguishers quickly. Signs should be placed high enough to be visible over furniture, equipment, and stored materials. Red backgrounds with white text are the industry standard.

Cabinets and recesses: Extinguishers may be placed in wall cabinets or recessed into walls, but the cabinet must not be locked unless a break-glass panel or other immediate-access mechanism is provided. In areas with high theft or vandalism risk, alarmed cabinets are acceptable.

Accessibility: Extinguishers must not be blocked by stored materials, equipment, or furniture. Keep a minimum 36-inch clear zone in front of each extinguisher location. During inspections, verify that access paths remain unobstructed. This is the most commonly cited maintenance violation.

Inspection and Maintenance Schedule

NFPA 10 requires three levels of extinguisher maintenance: monthly visual inspections, annual professional maintenance, and periodic internal examination and hydrostatic testing.

Monthly inspections (can be performed by building staff): Verify the extinguisher is in its designated location, access is unobstructed, the pressure gauge is in the green zone, the pin and tamper seal are intact, there is no visible damage or corrosion, and the operating instructions are legible and facing outward. Record the date and inspector's initials on the inspection tag.

Annual maintenance (must be performed by a certified technician): Thorough examination of all mechanical parts, extinguishing agent condition, and expelling means. Dry chemical extinguishers require verification that the powder has not compacted. Stored-pressure units are weighed to verify agent charge. The technician attaches a new annual service tag with their certification number.

Internal examination: Every 6 years for stored-pressure dry chemical and wet chemical extinguishers. The extinguisher is discharged, disassembled, inspected internally for corrosion or damage, recharged, and returned to service. CO2 extinguishers require hydrostatic testing every 5 years. Water and foam units require hydrostatic testing every 5 years. Dry chemical cartridge-operated units require internal examination every 6 years and hydrostatic testing every 12 years.