Commercially speaking, in the UK they have to be checked annually, and signed.
Fire extinguishers should be inspected annually - by a suitably qualified person.
Yearly
The expiry time of a DCP fire extinguisher is usually around seven years. After this, the powder should be replaced. Additionally, these extinguishers should be checked yearly to ensure all parts are present and that the seals are intact.
Fire extinguisher
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.
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.
the base of the fire
"After the blaze, he checked the fire extinguisher to see if it had been properly used."
at the base of the fire
at the base of the fire
Downwind from the fire.
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.