When talking about powder fire extinguishers, the question is often raised; 'What is the difference between ABC Powder Extinguishers and Dry Powder Extinguishers'?
The answer is that the two terms are largely interchangeable, as most dry powder extinguishers these days are ABC powder extinguishers. To be more precise, the term 'Dry Powder' is the general term for a type of extinguisher whereas ABC powder is the type of powder used in most dry powder extinguishers. However, there are also other 'dry powders' available.
Here is an overview of the different powders available:
ABC Powder – Made up of ammonium or mono-ammonium phosphate mixed with other powders to improve the flow or add bulk. ABC powder is often referred to as general purpose or multi-purpose extinguisher powder and is capable to fight class A, B and C fires.
BC Powder – Sometimes referred to as standard powder, because it was common before ABC powder became the norm, is a sodium bicarbonate based powder.
Monnex Powder – A compound of potassium bicarbonate, highly effective on petrol and oil based fires. Monnex powder is expensive compared to BC and ABC powders.
Class 'D' Powder – These specialist powders are used on fires involving flammable metals, such as magnesium and lithium and are usually applied using a low velocity discharge wand that will drop the powder directly onto the fire. The powder itself melts to form a glassy layer, covering the fire and preventing oxygen from reaching the fuel while also absorbing heat.
The most common dry powder extinguishers in use are the ABC powder variety, as ABC powder is the cheapest to produce and offers versatility and exceptional knock-down power.