Dry powder extinguishers
23 November 2020
Some dry powder extinguishers can cause extensive damage if used in the wrong environment. Caution is required when using them.
Electronic equipment can be particularly sensitive to the powder used in some extinguishers, and, in any environment where moisture is present, the powder can develop into an acidic solution.
The dry powder released can contain a formula of ingredients, including mono-ammonium phosphate and ammonium sulphate, which has the potential to cause considerable damage to the fabric of the building and its contents. This is due to its corrosive and abrasive qualities.
All contaminated surfaces will have to be cleaned to restore the visual appearance of the building and to eliminate the risk of subsequent corrosive and/or abrasive damage.
Clean-up operations will involve vacuuming the powder, followed by appropriate restoration work using professional cleaning services (conservators will need to be used for protected buildings and churches).
Pipe work and electronic circuitry can be particularly susceptible to attack from corrosive deposit. High level surfaces should also be attended to carefully - to prevent future deposition of powder onto the area below, and damage to any stonework at high level.
What you can do
Be mindful of the dangers posed by the potentially corrosive contents of some dry powder extinguishers and the risks involved when they’re discharged.
Both carbon dioxide and water or AFFF (Aqueous film forming foam) portable fire extinguishers are suitable for most fire scenarios within a building. Where buildings have existing dry powder extinguishers, steps should be taken to ensure they are not located in inappropriate places, for example in close proximity to paintings and expensive furnishings.
We would also recommend replacing existing dry powder extinguishers with a suitable alternative extinguisher when they reach the end of their service life. This is usually highlighted during fire risk assessments.
Adopting such an approach, and avoiding the use of dry powder extinguishers can significantly reduce the consequences of any accidental or malicious use of extinguishers.