Fire extinguisher CO types have the test information stamped on the cylinder, all other types get a sticker on the back of the cylinder. Once dry, the units are recharged. Unlike the UK, the US does not rebuild extinguishers and replace valves at specific intervals unless parts are found to be defective, with the exception of halon. Halon types are often given new o-rings and valve stems at every internal maintenance to minimize any leakage potential. OEM equipment must be used for replacement parts for the extinguisher to maintain its UL rating. If parts are unavailable, replacement is recommended, keep in mind
Fire extinguisher equipment (such as first aid kits). Most licensing authorities have regulations describing the standard appearance of these signs (e.g., text height, pictographs used and so on). Photoluminescent fire extinguisher signs are made with nontoxic photoluminescent phosphor that absorbs ambient light and releases it slowly in dark conditions – the sign "glows in the dark". Such signs are independent of an external power supply, and so offer a low-cost, reliable means of indicating the position of emergency equipment in dark or smoky conditions. The luminance performance for life safety appliance location signs should meet the requirements of International Standard ISO 17398