Info What do the letters on an extinguisher stand for? The letters on an extinguisher are there to inform you as to what type of fire that extinguisher and chemical is design to suppress.  If you have any questions about what type of extinguisher you  need, feel free to give us a call at (210) 599-4222 or an e-mail   and a knowledgeable technician can assist as to the best one to  fit your needs.    How do I know if my fire extinguisher needs service? They are a few ways to tell. 1. If you have used the fire extinguisher.  Most extinguisher are reusable and can be refilled by a license personnel. 2.  Check the gauge on the extinguisher.  If the arrow is in the red, you need to have the extinguisher serviced to insure usefulness.   3.  Check the tag on the extinguisher.  The inspection tags are valid a year from the date punched out.  On the example tag on the right the date May 2010 is punched out.  Therefore the next inspection date should be in May of 2011.