The use of dry powder fire extinguishers indoors

In this post we look at the use of dry powder fire extinguishers indoors. Dry powder fire extinguishers are very versatile. They can be used on Class A, B and C fires and also on fires involving electricity. If this is the case why not just use this one type of fire extinguisher in the workplace? It will mean only one type of extinguisher is required and therefore save money. Additionally it would avoid confusion on which extinguisher to use on a particular type of fire. At first glance dry powder fire extinguishers seem like a one stop solution however is this truly the case? In this post we explores some of the pros and cons and then look at what the British Standards have to say.

powder fire extinguisher

Advantages of dry powder fire extinguishers

  • Low temperature use – dry powder fire extinguishers are great because they do not freeze outdoors in low temperatures. This is especially important in the winter months that we experience in the UK when temperatures can sink below freezing. 
  • High fire ratings – when you compare the fire ratings to other extinguishers it is quickly apparent that powder extinguishers have much better fire ratings. A standard 6L water extinguisher would typically have a 13A rating and 6L foam  21A / 144B. In comparison a 6KG powder extinguisher will typically have a rating of 27A / 183B twice that of water and better than foam. 
  • Multipurpose –  powder fire extinguishers can be used on Class A, B and C fires and also fires involving electricity. 

Disadvantages of dry powder fire extinguishers used indoors

  • Mess – setting off a dry powder extinguisher indoors creates a lot of mess. This may take a considerable amount of time and effort to clean up. Powder may also enter equipment through vents and fans and accumulate inside. To illustrate if used in a server room, it is likely that powder would actively be drawn into the equipment by the cooling fans. 
  • Visibility – discharging a dry powder extinguisher indoors reduce visibility. When discharged they can create a large cloud of powder that can hang in the air. This can have the same effect as smoke and obscure escape routes and fire exits. This is a particular problem where occupants of the building may not be familiar with the layout. 
  • Breathing problems – discharging a powder extinguisher indoors may cause breathing problems. People with chronic respiratory problems such as asthma and bronchitis may suffer lung irritation through inhaling the powder. This may pose a safety hazard as there is the potential to cause a medical emergency which compromises the safe evacuation of the building in the event of a fire.

BS5306

BS5306 Part 8 2012 acknowledges the problems associated with the use of dry powder extinguishers in buildings. It states that they should not generally be specified for use indoors unless a health and safety risk assessment deems this appropriate. As an example it would be unlikely that you could justify the use of powder extinguishers in an office. Water and CO2 extinguishers would likely cover the fire risks present without any of the negative aspects of power extinguishers. 

Summary

As can be seen, for most work places dry powder extinguishers are unlikely to be good choice for use indoors. If used indoors they would create a large amount of mess and may even pose a safety hazard. Exceptions to this would be places where their use could be justified by a risk assessment.  Some common examples would be workshops and garages where fire risks include running fuel fires or flammable gasses.