Yesterday, during our biannual equipment safety class, the instructor told us that the small onetime use extinguishers have a 12 year life. The date of manufacture is stamped or molded into the base of the extinguisher. The instructor also said that the onetime use dry chemical extinguishers need to be turned upside down and taped on to keep the powder from packing tight, that could cause a malfunction. Where I work, if the extinguisher is rechargeable then it is inspected once a year and pressure tested every 5 years by a fire extinguisher service company.