It depends upon what type of extinguisher it is.
Many refillable types must be internally inspected on one-year intervals. Others only after 3, 5 or 6 years.
NFPA 1 13.6.9 prescribes timetables for inspection, maintenance and recharging of portable fire extinguishers, for reference, although it is not universally adopted.
Yearly
Every year
Commercially speaking, in the UK they have to be checked annually, and signed.
Fire extinguishers should be inspected annually - by a suitably qualified person.
Flammable metals often require special chemicals to extinguish, assuming there are any. So, in fact, you WOULD use a "chemical extinguisher", but probably not an ordinary dry chemical extinguisher.
Toner needs to be refilled on a laserjet 4050n as needed. The machine will alert you when it is time to change or refill it. It depends on how often you use your printer.
Any and all fire extinguishers should be inspected at least once a month. If you live in an area of severe hot or cold temperatures, it is wise to inspect them more often.
When there's a fireWhen there's an inspectionYou should pretty much always have a fire extinguisher on a boat. This may not be necessary for some types of boats; it's kind of unlikely that an aluminium canoe or rowboat is going to catch on fire, for example, but on any boat powered by an engine you should have one (or more).
ABC, BC or C. It is often best to disconnect the electrical power and use an extinguisher appropriate for whatever type of fuel happens to be burning (A or B). Do NOT use a water-type A fire extinguisher on an energized electrical fire.
Depending upon what fire code is used and where the extinguisher is located, it should be checked monthly. In fact, a fire inspector can ask to see the records of the monthly tests, which are normally attached on a tag on each extinguisher. Modern codes are beginning to require automatic electronic monitoring of fire extinguishers.
Ah, a yellow star on a fire extinguisher usually indicates it is a Class K extinguisher, my friend. These are specially designed for putting out fires involving cooking oils and fats, often found in commercial kitchens. Remember, it's important to always use the right type of extinguisher for the specific type of fire to keep everyone safe and sound.
Get the extinguisher and have a good grip on it, pull the pin out of the handle, pull the hose/pipe/tube out if it has one, aim towards the center of the fire. Also, please make sure you are using the proper extinguisher type.