Air Pressure 2 : Air under pressure that is used to keep water out of dry pipe automatic sprinkler pipes or provide pressure in pressure tanks or fire extinguishers
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}