6 year fire extinguisher maintenance: which units need it, what it involves, and how the clock runs

What the rules actually say

The federal rule is OSHA 29 CFR 1910.157(e)(4). It says stored pressure dry chemical extinguishers that require a 12 year hydrostatic test are emptied and given the applicable maintenance procedures every 6 years. Non-refillable disposable containers are exempt, and when recharging or hydrostatic testing is performed, the 6 year requirement begins from that date. OSHA also says, in (e)(3), that stored pressure extinguishers "do not require an internal examination" at the annual maintenance.

NFPA 10 words the scope more broadly than OSHA. The Minnesota Department of Health, citing the 2010 edition, describes the rule as applying to stored pressure extinguishers that require a 12 year hydrostatic test, with dry chemical units given as the example, and points to section 7.3.1.2 for the procedure. Kansas State Fire Marshal guidance uses the same wording. In practice: a rechargeable, stored pressure unit on a 12 year hydro is on the 6 year cycle.

In the 2010 edition (as cited by the Minnesota Department of Health), 7.3.3.1 is the 6 year maintenance label. A 2020 NFPA staff guide that names no edition points to Table 7.3.3.1 for internal examination intervals. Check your state's adopted edition.

Which extinguishers need it and which do not

Clean agent units other than halon are not covered by the sources checked for this page, so follow the manufacturer's service manual for those. Cartridge operated dry chemical units also have their own treatment that varies by edition; the one point that holds across the sources here is that they are exempt from the verification of service collar (2010 edition, 7.3.3.2.2, per the Minnesota Department of Health).

The excluded types simply run on shorter clocks. A 5 year hydrostatic test includes an internal examination: OSHA 1910.157(f)(3) requires cylinders and shells to be examined internally, as well as externally, before the test. So those units are opened at least every 5 years anyway.

What the procedure involves

NFPA 10 sends the technician to the manufacturer's service manual for the internal examination steps, so the manual for the specific model is the procedure. As an example, the Amerex manual for its stored pressure dry chemical model 05602 lays out the "six year teardown" roughly in this order:

1. Discharge the agent and pressure into a closed dry chemical recovery system and confirm the unit is completely empty and depressurized.
2. Clean the unit, check that the nameplate is secure and legible, and inspect the cylinder for corrosion, abrasion, dents or weld damage. If there is doubt about cylinder integrity, hydrostatically test it.
3. Look for damaged, missing or substitute parts, and check the manufacture date on the nameplate against the 12 year hydro.
4. Inspect and, if needed, replace the gauge, ring pin, discharge lever, carrying handle, nozzle or hose and horn.
5. Inspect the valve assembly for corrosion or damage to the nozzle or hose threads, then remove and disassemble it (downtube, spring and valve stem) and fit a new valve stem and collar O-ring.
6. Finish with steps 3 through 14 of the manual's recharge procedure. The verification of service collar then goes on, because NFPA 10 requires one after any internal examination (see the next section).

Other Amerex manuals add two notes worth knowing. The 05617 manual warns that "some states have legislated a 'complete maintenance' on an annual basis," so a state rule can be stricter than the 6 year federal interval. The 05616 manual points out that the verification of service collar "can only be installed if the operating valve has been removed," which is exactly what makes the collar useful evidence.

While the unit is out of service, OSHA 1910.157(e)(5) requires alternate equivalent protection, and NFPA 10 (2010 edition, 7.1.3, per the Minnesota Department of Health) expects a replacement suitable for the hazard and of at least equal rating.

The label and the collar

Two records go on the extinguisher. Our Fire Extinguisher Inspection Checklist (Monthly and Annual) page lists the basic contents; here are the details that trip people up, all from the 2010 edition as summarized by the Minnesota Department of Health.

• 6 year maintenance label (7.3.3.1): metallic or similarly durable and weatherproof, at least 2 by 3.5 inches, with the month and year punched, the name or initials of the person and the company name (7.3.3.1.3).
• Heatless process (7.3.3.1.1): the label goes on the shell by a heatless process, and old maintenance labels are removed when a new one is applied.
• Verification of service collar (7.3.3.2): required on every unit that has had an internal examination or a recharge. It must not be removable without taking off the valve, and it shows the punched month and year and the company name.
• Annual tag (7.3.3): the annual tag still applies, so a 6 year visit usually updates the tag, adds a label and adds a collar.

State rules can go further. Florida rule 69A-21.237(2)(b) requires the 6 year record decal to be metallized or equally durable and "self-destructive when removal from an extinguisher shell is attempted." For the full Florida picture, see our Florida Fire Extinguisher Tag Requirements (FAC 69A-21) page.

How the 6 year count runs

The federal text tells you what restarts the clock but not where it first starts. Florida spells it out: under 69A-21.237(2)(a), the interval "shall begin from the date of manufacture of an extinguisher and, once maintenance has begun, from the date of recharging and/or internal maintenance of an extinguisher." Florida also requires complete 6 year procedures whenever a covered unit "is opened for any purpose." Kansas and the Amerex manuals word the reset as applying when the maintenance procedures are performed during periodic recharging or hydrostatic testing.

The practical rule for a service company: track three dates per unit, the manufacture date from the nameplate, the last 6 year or internal maintenance, and the last hydro. The next 6 year is due 6 years after the latest of the events that restart it. The 12 year hydro is counted separately, from the manufacture date for the first test (the Amerex 05602 manual has the technician check the nameplate manufacture date against the 12 year test) and from the previous test after that, and a hydro also restarts the 6 year count. To work out the next hydro and 6 year dates for a specific extinguisher, use the expiration date checker.

Notice what happens without a reset: a unit that is never discharged gets its 6 year maintenance at year 6 and its hydro at year 12, and the hydro at year 12 restarts the count, so the next 6 year falls at year 18. A recharge in between (under the NFPA wording, one that includes the maintenance procedures) shifts the 6 year date but never the hydro date.

Common mistakes

• Putting CO2, water or wet chemical units on a 6 year schedule. They run on 5 year hydro and their own internal examination intervals.
• Doing a 6 year on a disposable unit. Nonrechargeable units are exempt and are retired 12 years after manufacture.
• Forgetting that a recharge done with the full maintenance procedures restarts the count, or recharging without installing a collar.
• Leaving an old 6 year label on the shell under the new one, which the 2010 edition says to remove.