With their low prices and ease of use, aerosol fire sprays are a tempting purchase. But the sprays are no substitute for a fire extinguisher. In fact, in Consumer Reports’ tests the sprays sometimes made a grease fire flare up, which could make it spread. Performance problems caused us to judge two aerosol fire sprays—the First Alert AF400 Tundra Fire Extinguishing Spray and Shield Fire Protection Kitchen Guard—Don’t Buy: Performance Problem. Now we’ve found a third brand being advertised called Knockout 360 that’s also an aerosol fire spray.
None of the sprays has a pressure indicator that shows whether the unit is ready for use. Although their labels state that they are not intended to replace a standard National Fire Protection Association compliant fire extinguisher (NFPA 10), that statement can be easily overlooked. The sprays have a relatively short shelf life of three years as opposed to six to 12 for dry chemical units. We recommend that you pass on the Knockout 360 and any other fire fighting spray that lacks these key features and buy a conventional fire extinguisher with a gauge that meets NFPA 10 requirements.
When it comes to fire extinguishers, the general rule is to always buy the largest model that everyone in the household can handle. They contain more flame retardant and in our past tests could deliver it quicker and longer. To be fully protected you should have one full-floor multipurpose fire extinguisher on each level of your home, one in the garage, and smaller supplemental models for the kitchen and car.
Fire extinguishers are categorized by letters and numbers. The most common letter types are A, B and C. A is meant to put out such combustibles as wood, paper and cloth. B is for flammable liquids and gasses such as kerosene, oil and gasoline. And C is for electrical fires and equipment such as televisions and wiring. The number preceding the A designation is the amount of retardant or capacity of the extinguisher. So a 2A extinguisher would contain the equivalent of about 2-1/2 gallons of water, a 4A would have double the capacity. The number preceding the B designation indicates the approximate square footage the extinguisher can handle. A 40 B means it can put out a 40-square-foot fire. The C designation does not have a corresponding number and simply means the retardant is non-conductive and can be used on electrical fires.
Most full-floor extinguishers will have a 2A to 4A designation and 10B to 60B designation. Supplemental extinguishers for the kitchen may sometimes lack an A designation and have a 5BC to 10BC rating. Finally, only use a fire extinguisher when the fire is small and not growing, the fire is not between you and an exit, and after you have already evacuated the house and called the fire department.
—Mary H.J. Farrell