The honest answer is that you can't count on it at all. Once an extinguisher has been used, even for a one-second squeeze, it's out of service until it's recharged or replaced. There's no such thing as a partly used extinguisher you can trust.
That surprises people, because the extinguisher usually still feels heavy and the gauge might still be in the green. Here's why that doesn't mean much.
Why one squeeze is enough
When you squeeze the handle, the valve opens. When you let go, it's supposed to close tight, but dry chemical powder can get caught in the valve and keep it from sealing all the way. The pressure can then leak down slowly over days or weeks. You can hang it back up looking fine and find out it's empty the day you need it.
The gauge won't tell you how much agent is left, either. It only shows pressure. An extinguisher can read good pressure with a lot of its powder gone, and a typical extinguisher only runs for a few seconds to begin with. You don't want to find out in the middle of a fire that yours had a couple of seconds left in it.
What counts as used
Any discharge counts, no matter how small:
- A real fire, even one that went out right away
- A quick test shot to see if it works
- Somebody bumping the handle
- A training discharge
- A missing pin or a broken seal, which you should treat as used until somebody checks it
What to do after it's used
Take it off the wall so nobody grabs it thinking it's good, and don't hang it back up. If that spot can't be left empty, move one of the same type over from nearby until yours is back. Make a note of when it was used and why.
Then call us. We recharge on site when we can. Our trucks carry loaners. If an extinguisher has to come back to the shop, a loaner goes up in its place until yours is back.
What a recharge involves
A recharge is more than topping it off. The tech empties what's left, takes the valve off, and checks the cylinder and the valve. Then the O-ring gets replaced, the extinguisher is filled with the right agent by weight, and it's pressurized to what that extinguisher was built to hold. When the valve comes off a stored-pressure extinguisher, a new verification collar ring goes on under it. That ring is your proof the work was done.
If you've wondered why this isn't a do-it-yourself job, we wrote that up in can you refill a fire extinguisher yourself.
Rechargeable or disposable?
Most commercial extinguishers have a metal valve and a gauge, and they're made to be recharged. The small ones with a plastic valve, the kind sold for homes, are usually disposable. They're made to be used once and replaced. If you're not sure which kind you have, we'll tell you when we see it.
Sometimes a recharge isn't worth it. If the cylinder is dented or rusted, the valve is damaged, or it's an older unit that would cost more to test and recharge than it's worth, a new one makes more sense. The tech will tell you which way to go.
What about one that's never been used?
An extinguisher that's never been used doesn't have an expiration date. It has a service schedule. It gets a monthly look and a yearly inspection and service. Every six years, a stored-pressure dry chemical extinguisher is discharged and gets an internal examination before it's recharged. The cylinder also gets a hydrostatic test every 5 or 12 years, depending on the type. As long as it keeps passing, it stays in service. The whole schedule is in how often do fire extinguishers need to be inspected.
On a boat, a truck, or a machine
The same rule holds on a boat, in a truck, or on a piece of equipment. Once it's been used, it comes off until it's recharged, and that spot needs another extinguisher until it's back.
If you used one today, call 1-800-348-9604 and tell us how many got used and where. We leave a report. We keep up with the due date so you don't have to.