Fire extinguisher five categories. In the UK the use of Halon gas is now prohibited except under certain situations such as on aircraft and in the military and police. Fire extinguishing performance per fire class is displayed using numbers and letters such as 13A, 55B. EN3 does not recognise a separate electrical class - however there is an additional feature requiring special testing (35 kV dielectric test per EN 3-7:2004). A powder or CO extinguisher will bear an electrical pictogramme as standard signifying that it can be used on live electrical fires (given the symbol E in the table). If a water-based
Fire extinguisher coverage area is about . One benefit of this type is that it may be used for passive suppression. The ball can be placed in a fire-prone area and will deploy automatically if a fire develops, being triggered by heat. They may also be manually operated by rolling or tossing into a fire. Most modern extinguishers of this type are designed to make a loud noise upon deployment. This technology is not new, however. In the 1800s, glass fire grenades filled with suppressant liquids were popular. These glass fire grenade bottles are sought by collectors. Some later brands, such as