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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: K Lard on September 29, 2020, 09:17:32 AM
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Are dry powder extinguishers safe for use over 1000V? Some commercial sites state this, but I can't find anything official and there is no max voltage on the extinguishers themselves. Any info would be gratefully appreciated.
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Yes, they are assumed to be electrically safe, just like CO2 & vapourising liquids, without needing the 35,000V di-electric test. Note that any extinguishing agent can only be marked as safe for electrical fires up to 1000V at 1m under EN3, it's just that most UK supplied extinguishers don't follow EN3 by not having the "suitable for" clause written on and using the unofficial "lightning bolt" pictogram instead.
The current Fire Service Manual permits the use of powder, CO2 or VL regardless of voltage - the main issue with fires over 1000V are the general safety risks and this is why there is a limit on extinguishers for everyday users. Persons with specialist electrical safety knowledge may be able to safely tackle high voltages.
Oddly enough, back in the 70's & 80's, where a lot of powder extinguishers were Sodium Bicarbonate based (now they are Ammonium Phosphate based) some safety signs of the time did say powder was suitable for low voltages and CO2/VL was suitable for high voltages!
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Thank you for your full and detailed answer!!!