NFPA 10 – 1998 Edition states under Section 4-4 Maintenance: “4-4.2* Procedures. Maintenance procedures shall include a thorough examination of the three basic elements of a fire extinguisher:
(a) Mechanical parts
(b) Extinguishing agent
(c) Expelling means”
While CO2 extinguishers do not require an internal examination, and the agent itself is also the expelling means, all mechanical parts must be checked.
Most 5 lb. CO2 extinguishers have a horn attached to a discharge tube which is attached to an elbow that swivels. The horn must be from the original manufacturer, or the extinguisher may fail to discharge properly. The elbow must swivel correctly in order to use the extinguisher safely and effectively.
Amerex horns must be used on Amerex Extinguishers, and only on Amerex Extinguishers. Using parts from manufacturers other than Amerex may cause the extinguisher to function improperly, or not at all, in addition to voiding the U.L. listing and the Amerex warranty.
While performing maintenance on a 5 lb. CO2 with a swiveling elbow and discharge tube, it is necessary to confirm that the elbow swivels properly and does not bind. For a more definitive list of what must be checked refer to Table A-4-4.2(a) “Mechanical Parts Maintenance Checklist in NFPA 10.