Chemical additives can radically increase the effectiveness of a water fire extinguisher by up to 300%, as well as reducing the size of extinguisher required. Water additive fire extinguishers, often referred to by Chubb Fire’s brand name of Hydrospray, are smaller and lighter than standard water fire extinguishers.

A 3 litre Hydrospray Elite extinguisher matches the 13A rating of an ordinary 9 litre water extinguisher and, if you have ever picked up a 9 litre extinguisher, you’ll understand the benefit. A 6 litre water additive will normally have a 21A rating. As premises need a minimum of 13A, these have become extremely popular.

Water additive extinguishers are still solid red in colour, and bear the usual rating and safety marks.

How Water Additive Fire Extinguishers Work

The additives work by removing water’s natural surface tension, making the water ‘wetter’ or ‘stickier’, so it adheres to and soaks into the burning materials more effectively. Can you remember school chemistry experiments with water tension and then adding detergent to break the tension down?

The additive extinguishers also has a special spray nozzle attached that atomizes water and spreads it in a more effective arc than a conventional nozzle. In addition, the nozzle enables safe use in the vicinty of (but not directly on) electrical equipment. They will have passed the BSi 35,000V dielectric test to BSEN3-7:2004, just in case.

What’s Special About a Hydrospray Fire Extinguisher?

Since ‘Hydrospray’ fire extinguishers operate at a higher pressure than standard water fire extinguishers (15bars), they are available in smaller, high grade steel cylinders of 3 litre and 6 litre capacity.

This makes them much easier to handle and lighter to lift, and with a modern external coating of epoxy polyester, they are also scuff and dirt resistant. Inside, the cylinder is lined with polyethylene to prevent the inside of the fire extinguisher corroding.

The 3 litre version weighs just 5.5kgs, yet easily equals its 9 litre water-only equivalent’s 13A rating. The 6 litre weighs 10kg and earns a 21A fire rating, thanks to its increased efficiency. A standard 9 litre version tops the scales at 15kg.

Water and Electricity

Water conducts electricity, so non-additive water should never be used near exposed live electricity cables. High quality water additive nozzles have passed the 35kv conductivity test, so can be used with minimal risk near (but never directly on) electrical equipment.

For the best protection in an office or retail environment, water additive extinguishers are usually provided alongside a CO2 fire extinguisher to make the best combination.

Water Additive on non-Class A Fires

These modern marvels should only be used on Class A fires, although unlike the simple water extinguishers, they have a safety nozzle. Both types of water fire extinguisher, however, are actually more dangerous if used on other classes of fires.

The jet of water will, for example, simply spread a Class B fire of flammable liquids over a larger area, whilst the same action will scatter the burning metals of a Class D fires, causing more fires to erupt. Equally, never use any extinguisher other than wet chemical on a Class F fire, as this is extremely dangerous.

What’s In a Name?

Once Chubb Fire has devised and effectively marketed their Hydrospray and Hydrospray Elite, other manufacturers came out with similar models so you may find a TurboSpray, AquaPlus, WaterPlus, Ecojet and other wacky names.