BAFSA Highlights Concerns Regarding Electrocution Due To Water Fire Extinguishers Or Hose Reels Use In Live Electrical Equipment

Discussions with architects, developers and others, as well as main contractors when discussing areas of a sprinklered building frequency relate to areas where sprinkler protection can be omitted. One concern often raised with the British Automatic Fire Sprinkler Association (BAFSA) is the possibility of injury or damage when sprinkler protection is installed in electrical utility rooms. 

BS 5306 Part 0 standards

The forthcoming iteration of BS 5306 Part 0 standards contains advice on the interactions between electricity ad fire suppression systems, including hose reels and portable fire extinguishers. The text quotes from an article published in the November 2018 issue of Fire Risk Management, the journal of the Fire Protection Association.

Concerns about the dangers of using water fire extinguishers or hose reels to extinguish fires in live electrical equipment usually relate to the possible risks of electrocution. This theoretical risk (the Health and Safety Executive (HSE) have not recorded any such actual injuries) probably originates in tests undertaken by the Paris Fire Brigade in the 1930s and replicated in a piece of demonstration equipment at the Fire Service College.

Omitting sprinkler protection in plant rooms

The conventional approach at the time of publication of BS 5306 was to omit sprinkler protection in plant rooms

Using a 9 liter water extinguisher generating a straight jet could endanger the user, if the jet were to come into contact with a live conductor, as there is the possibility that electricity could be conducted back upstream to the person holding the extinguisher, especially if they are standing on a wet floor.

Because of this risk, the conventional approach at the time of publication of this part of BS 5306 was to omit sprinkler protection in plant rooms and to provide dry powder and/or carbon dioxide portables adjacent to electrical equipment.

Portable fire extinguishers using water mist

Portable fire extinguishers using water mist have been available in the United Kingdom for a number of years now, however, they do not appear to have been widely promoted or deployed in commercial and industrial applications. Apart from their widespread effectiveness, portable fire extinguishers using water mist have a major advantage in that they have a high level of dielectric safety.

A number of manufacturers of portable water mist fire extinguishers on the market in the United Kingdom state that their product has passed a 35 kV test. There have been several instances where fires have started in server rooms and have been extinguished by a single sprinkler head, preventing any fire spread from the room of origin.

BS 5306, the standards for sprinklers and water mist systems

It is normal practice to install inert or chemical gas flooding systems where automatic fire suppression is essential

At the time of publication of this part of BS 5306, the standards for sprinklers and water mist systems allow these to be omitted in areas or rooms where water discharge might present a hazard. For sprinklers, in particular, BS EN 12845:2015, 5.1.3c standards is used based on the systems to be subject to a risk assessment, where their use is proposed in areas where electrical fire or electrocution risks are present.

Where wet systems are clearly unacceptable because of the risk to personal safety or collateral damage to property, it has been normal practice to install inert or chemical gas flooding systems where automatic fire suppression is essential.

Water-based fire suppression equipment

With regard to water-based systems in general, power generation companies make extensive use of water-based fire suppression equipment to protect turbo-alternators, switch gear and transformers at voltages up to 400 kV and involving significant currents (typically 20, 000 MVA).

Provided that such systems are designed and installed in accordance with the appropriate standards, it is expected that they will function as designed to justify omission of coverage in switch rooms, server rooms and transformer chambers.

Risk of electrocution in fire extinguisher use

In an article in the FPA magazine, FRM (November 2017), former BAFSA Secretary General, Stewart Kidd was quoted as stating, “I have long believed that the frequently expressed concerns about ‘mixing water and electricity’ are greatly overstated and usually relate to a theoretical possible risk of electrocution while using a fire extinguisher or hose reel. Much of the fear may relate to the demonstration of the potential for conduction of high voltage at the Fire Service College.”

I can find no records of any actual injuries relating to the use of extinguishers being incurred since 1945"

Stuart adds, “I can find no records of any actual injuries relating to the use of extinguishers being incurred since 1945. The Health and Safety Executive (HSE) records confirm that, since 1996 (as far back as its records go), none of the fatal electrocutions recorded relate to fires or firefighting.”

Danger of conventional water extinguishers

The fear of electrocution presumably relates to the use of conventional, 9 liter water extinguishers, which produces a ‘straight jet’. If this was to come into contact with a live conductor, there is, it is agreed, at least a possibility that electricity could be conducted back down the stream to the person holding the extinguisher, especially if they are standing on a wet floor.

As mentioned earlier, there aren’t any examples of this happening and the HSE has confirmed that it is not aware of any such accidents being reported.

That said, do water mist extinguishers that are usually rated as ’safe at 1000v’ (and most are tested to 35kV) pose this hazard, in relation to tackling a fire in live electrical equipment? Is it not time that BS 5306 Part 8 Selection and installation of portable fire extinguishers: Code of practice was updated to reflect the benefits of portable extinguishers using water mist? These are few of the important questions to be answered.