Hydrotesting is not necessary for which type of extinguishers?

Hydrotesting is a procedure used to test the integrity and strength of a fire extinguisher's cylinder. It's typically required for extinguishers that are made of metal and can withstand high pressure. Water-based extinguishers are often not subject to hydrotesting because they use pressurized gas to expel water, and their maintenance requirements are generally less stringent than those for cylinders that contain dry chemicals or foam. The regulations for water-based extinguishers often allow for visual inspections to be sufficient for ensuring their functionality.

In contrast, foam extinguishers, dry chemical extinguishers, and aerosol extinguishers often require hydrotesting due to the nature of their construction or the materials they contain. These types of extinguishers may hold pressurized agents that require regular checks for safety and functionality, necessitating hydrotesting to identify any potential weaknesses in the cylinder. Thus, the maintenance standards differ based on the content and construction of the fire extinguishing devices.