Don’t compromise on safety!
A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-control fire, such as one which endangers the user (i.e., no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire department.
It is therefore imperative that the equipment being used is effective and has fast “knock down” characteristics to prevent the fire from getting out of control. Fire extinguishers are rated according to their capability by extinguishing pre-determined sizes of fires and this is called the “Fire Rating” of the particular extinguisher. Test methods for assessment are prescribed in the SABS standard SANS 6172 – Fire extinguishers ― Assessment of fire rating and the rating is done on class A (normal combustibles) and class B (Flammable liquid) fires.
The most commonly used extinguisher is the general purpose ABC Fire class Dry Chemical Powder (DCP) extinguisher. The active ingredient in these extinguishers is Mono Ammonium Phosphate (MAP) and the percentage of this ingredient is normally 40% (Std), 70% or 90%. The higher the percentage of MAP content the more effective the extinguisher will be. In high hazard industry such and mining and petrochemical applications 90%MAP extinguishers are normally prescribed. Typically a 40% MAP 9kg DCP extinguisher will have a fire rating of 27A144B while the same size extinguisher with 90% MAP will have a fire rating of 43A233B! For purposes of explanation, a 233B rated extinguisher has been tested and extinguished a fire made in a 3m diameter pan containing 155L of burning Heptane while a 144B rated extinguisher will have been tested to extinguish a maximum fire size of 96L of burning Heptane in a 2.4m dia. pan.
A standard SABS approved 1.5kg DCP extinguisher as prescribed for motorsport use, will have a minimum fire rating of 5A21B. Recently promoted disposable portable condensed aerosol fire extinguishers will commonly only achieve a rating of 3A13B. This equates to it actually successfully extinguishing a fire made with 8.66L heptane in a pan with diameter 0.72m. This is really a far cry from the capability of a 9kg DCP extinguisher and only just over half as capable as a 1.5kg conventional SABS approved DCP extinguisher which will be capable of extinguishing a 14L heptane test fire, so do not be fooled by marketing talk and discharge time duration claims. The actual fire rating achieved by a particular size of extinguisher charge mass must be one’s the factual reference for fire extinguishing performance.
These condensed aerosol extinguishers do have advantages in their compactness but disadvantages in that they are of aerosol type and not as effective in windy conditions or when a greater distance of discharge is required. Never mind the fire rating performance when compared to conventional general purpose extinguishers.
When thousands are being spent in money and TIME on an expensive commodity, one should at least have the peace of mind that when one meets the minimum requirement for fire protection it is going to be the better / safer/ more effective option.