Extinguishers, fire hoses and other fire safety equipment (alarms, exit signs, emergency lights) need to be checked on a regular basis to ensure they are in working condition.
Typically a quick visual check is to be done at least monthly by an employee or the monitor in the area. Under law, extinguishers and hoses must be checked and documented at least once a year by a qualified inspector. They also must have a sign-off tag (or other documentation) to verify that they have been inspected.
Extinguishers must be recharged anytime that they have been used, if the pin has been pulled (seal broken), or the gauge is not in the proper pressure area. Even if an extinguisher was only used a small amount it must be serviced as the used powder clogs the valve and prevents reuse.