Self-adhesive vinyl signs and labels are silk screened with UV inks then clear laminated for durability and fade resistance. Mounting surface must be clean, dry, smooth and non-porous (Brick, cement block, etc. is porous). If in doubt use aluminum or plastic signs.
 
Signs are designed to conspicuously mark the location of the fire extinguisher. If you do need to mount them on a porous surface, such as cement block, try an aerosol adhesive for extra adhesion.