Diffusion Pump 2 : A vapor pump that has boiler pressures less than a few torr and is capable of pumping gas at intake pressures 20 millitorr or less and discharge pressures 50 millitorr or less
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}