USCG Sector Hampton Roads issued a Safety Alert regarding compatibility of CO2 fire extinguisher components. During the fighting of a small shipboard fire, a CO2 extinguisher failed to operate properly. Fortunately, a second fire extinguisher accomplished the job. Investigation revealed that an obsolete and incompatible diffuser had been installed in the CO2 extinguisher at some time in the past. It is recommended that fire-fighting servicing companies check all CO2 extinguishers for compatibility of parts on a regular basis. (3/5/14).