Water extinguishers to be used with care

Ask the average person in the street what a fire extinguisher contains and the odds are water extinguishers will come top of the list. The problem is that although water has been used to extinguish fires for millennia the types of fire a water extinguisher can tackle are very limited particularly in a home or office environment. These limitations are not widely appreciated by the general public who mistakenly see water as a catch all solution for fire fighting.

In practice water extinguishers should only be used for tackling fires involving common combustible materials like wood, paper and similar solids collectively termed Class A fuels by fire safety professionals. However there are some fairly common solids specifically metals like magnesium, aluminium and sodium that water will not extinguish effectively although fortunately such fires are rarely encountered outside specialist manufacturing facilities.

More common are fires involving flammable liquids like petrol and oil. Using a water fire extinguisher on such fires is a useless endeavor and potentially dangerous. Burning liquids will simply float on the water, as the water runs off it carries the fuel with it spreading the flames further. Similarly water fire extinguishers have no effect on burning flammable gases like butane propane and natural gas as the water molecules are too large to displace the air borne oxygen supporting the combustion process. It is for this reason that fires on oil rigs are so difficult to extinguish even though they are literally surrounded by water. At best applying water will merely prevent fire spread in the solid structure.

Also common in the home and at work are fires in electrical equipment from televisions and cookers to computers and photocopiers. Once again using a water fire extinguisher has some major drawbacks. Firstly if it is not possible to turn off the power, or more likely, if in the heat of the moment (pardon the pun) you forget to do so, then selecting the red labeled water extinguisher from the fire point is to put your life at risk. The water will quite probable suppress or even extinguish the fire but it is also a great conductor of electricity. The continuous jet of water between the extinguisher in your hands and the target fire connects you to the electricity coursing through the equipment. End result electrocution!

Even if you have the presence of mind to switch off the power applying water to electrical equipment you will further damage circuitry and electronics and may contaminate other equipment like your digital box or a printer not directly involved in the fire making the chances of repair minimal and the asset losses greater.

You should also be wary of using water extinguishers in the kitchen environment. Spraying a burning cooking pan with a high pressure jet of water is a recipe for disaster. For one the water jet will likely splatter and spray the burning fats around the kitchen spreading the fire. Secondly however hard you try the water will not extinguish the fire as like petrol the fat will just float on top, the pan will overflow further and the fire will spread.

When used for common Class A type fires water outshines any other type of extinguisher for economy and efficiency but knowing its limitations will ensure the safety of you, your family and work colleagues.

Powder Extinguishers – things to know

Powder extinguishers also known as Dry Chemical and Dry Powder fire extinguishers are widely available and commonly found in virtually every business premises. What is possibly not widely appreciated is that Dry Powder is a catch all description for a group of fire extinguishers that use different types of chemicals each of which have different fire fighting capabilities. To simply purchase one of the many dry powder extinguishers available at discount prices all over the web simply based on the generic name could be a costly mistake if you choose the wrong Dry Powder.

The commonest misconception is that a multipurpose ABC Dry Powder for use on Class A, B and C fires is somehow just an upgraded BC Powder extinguishers.

A class BC extinguisher contains Sodium Bicarbonate and came into use in the late 1920′s to tackle flammable liquids and gases now called Class B and Class C fire respectively. They could also be described as the first Carbon Dioxide extinguisher as in the heat of the fire the Sodium Bicarbonate undergoes a chemical reaction that produces a cloud of carbon dioxide that drives off the oxygen smothering the flames.

Just like actual Co2 extinguishers it is not reliably effective on Class A fires involving solid combustibles as once the gas dissipates and the air oxygen returns the retained heat in the fuel can cause re-ignition. Flammable liquids and pressurised flammable gases retain little heat so do not re-ignite.

ABC fire extinguishers on the other hand contain ammonium sulphate. They are effective on solid combustibles because the heat of the fire causes the powdered chemical to melt even at a relatively low temperature. The effect is to smother the fire and form a continuous barrier layer preventing oxygen reaching the fuel.

Generally a BC rated extinguisher will outperform a multipurpose ABC of the same size on flammable liquids and gases.

Another fire extinguisher powder to look out for is Potassium Bicarbonate which has double the fire fighting capacity of sodium bicarbonate on Class B flammable liquids. Potassium Bicarbonate and Urea Complex is better known, in the UK at least as Monnex Dry Powder. Its superior performance makes it the extinguisher of choice for the oil and gas industry and interestingly in motor sports such as Formula 1 due to its ability to knock down high octane fuel fires. In the heat of the fire the Monnex powder fragments into smaller particles creating a larger surface area for free radical inhibition a process that should really be viewed as the fourth element of a fire tetrahedron together with the Oxygen, Fuel and Heat we associate with the Fire Triangle. Again Monnex is not effective on Class A fires.

So when choosing Powder Extinguishers make sure you assess the fire risk you are trying to safeguard and choose the extinguisher best suited to the task.

Co2 Extinguishers – Things you should know

Co2 extinguishers originally came into prominence as a replacement for halon or BCF extinguishers which were banned for most applications in 1993 under the Montreal protocol after it was discovered that halons had the highest ozone-depleting capacity of any chemicals in common use.  Co2 extinguishers contain liquefied carbon dioxide under extreme pressure and are notable for not having a pressure gauge on the canister and a hard flute shaped discharge horn. In the UK they are also colour coded with a black panel.

Carbon dioxide extinguishers suppress fires by displacing oxygen thereby taking away the oxygen element of the fire triangle. Although carbon dioxide is very cold as it comes out of the extinguisher, this does not mean they are suitable for Class A fires involving solid combustibles like paper, wood and fabrics as insufficient oxygen may be displaced to successfully put the fire out. Class A materials may continue to smoulder and may re-ignite.

Carbon dioxide fire extinguishers are primarily intended for use on Class B fires which include flammable liquids such as petrol, oil, diesel, (excluding cooking oil), some solid fuels like wax. In addition as carbon dioxide is also non-conductive and unlike powder and foam leaves no harmful residue that may damage or contaminate sensitive circuitry they are commonly recommended for fires involving electrical equipment. Co2 extinguishers are not effective on flammable gases.

The combination of properties of Co2 have applications in laboratories, clean rooms, engine compartments, generator rooms, boats and flammable liquid storage areas. They are also commonly found in offices and server rooms containing computer equipment.

Although they are rated for use on flammable liquids they should not be used on cooking oil fires as the ice cold high pressure discharge will splash the burning and spread the fire further.

Carbon dioxide extinguishers are not really suitable for dealing with fires outside as the gas quickly disperses, so are generally restricted to indoor use. On the other hand be aware that carbon dioxide replaces the oxygen in the air which can lead to asphyxiation when discharged in confined spaces, so take care to ventilate the area as soon as the fire is under control.

Advantages of Foam Fire Extinguishers

Foam fire extinguishers, or more correctly AFFF extinguishers offer some key advantages over the better known water equivalents. AFFF is short for Aqueous Film Forming Foam and, although it contains water as a primary element, when applied to a Class A fire involving combustible solids Foam extinguishers not only cool the burning material but also form a chemical barrier or film that separates the flames from the airborne oxygen necessary to support combustion.

Weight for weight AFFF is a substantially more effective fire suppressant than water. A 6 litre foam fire extinguisher has the same fire rating as a 9 litre water both of which carry a 13A approval. The net difference in weight is close to 4kg or 9lbs in old money. Certainly for commercial offices, businesses and residential blocks this provides an opportunity to utilise this advantage to install more manageable lighter weight units without compromising on fire safety.

There is also a cost saving to be gained by opting for a foam extinguisher as at the time of going to press our standard 6 litre foam fire extinguisher is just £22.50 compared to £25.25 for the 9 litre water as a high proportion of the ex- works cost is in the canister itself.

If weight and cost and saving were not enough unlike water the film forming properties of AFFF foam extinguishers make them highly effective at combatting Class B flammable liquid fires, typically petrol, diesel , paints and solvents. A 6 litre foam fire extinguisher has an impressive 144B rating. This added versatility makes them ideal for garages and petrol forecourts and they are the extinguisher of choice for motor sports in general. On a much larger scale AFFF foam is also used extensively at airports applied from large mobile extinguishers or tenders to form a fire suppressive blanket.

Boat, caravan and recreational vehicle owners can also take advantage of this versatility with models now available in 1 and 2 litre capacities.

Fire extinguisher bought at car boot sale is false economy

When it comes to Fire Extinguishers I like to think I am pretty clued up on Standards and legislation and at Fire and Safety Centre we have invested a great deal of time in trying to educate our customers regarding compliance issues particularly post the introduction of the Regulatory Reform (Fire Safety Order) 2005 the RRO. Clearly getting the message across to some businesses on how to select the right Fire Extinguishers has some way to go if my casual observation last Sunday is any measure.

Since the demise of our local village shop I am obliged to visit the next village to collect my Sunday newspaper. In so doing I pass the regular Sunday morning car boot sale in the same village. As I drove through I noticed a chap leaving the car boot lugging a red fire extinguisher.  I only caught a passing glance but thought it unusual to find fire extinguishers for sale on a car boot.

The newsagent is just a couple of hundred yards from the car boot and as I left the shop the chap with the extinguisher had caught me up. He was outside another shop in the arcade and had placed the canister on the ground whilst he unlocked the door so I had a better look as I returned to my car. It was clearly a 6 litre water extinguisher but I could see no BS EN3 kitemark or even a CE mark and worse still the safety pin was missing.  I recognised the new owner as the proprietor of the shop which is a cafe and chippy which I visit occasionally when we fancy fish and chips.

Now it could be that the extinguisher was intended for some legitimate purpose even though it was clearly not fit for purpose, but the idea of a water extinguisher in proximity to scalding hot fat made me more than uneasy. There is a big difference between genuine approved kite marked budget fire extinguishers as found on our web site and car boot seconds of suspect provenance. The few pounds he may have saved may cost him thousands if the fire inspector calls and finds his “bargain” deployed in the shop. I regret to say I walked on by without putting him in the know but will be on the lookout the next time I call in and may summon the courage to mention the potential pitfalls.