Positive Pressure SCBA : An SCBA in which the pressure inside the facepiece, in relation to the pressure surrounding the outside of the facepiece, is positive during both inhalation and exhalation
NFPA 1981 Standard on Open-Circuit Self-Contained Breathing Apparatus for Fire and Emergency Services, 2002 ed. https://www.nfpa.org/assets/files/AboutTheCodes/18 52/1852-F2007-ROP.pdf, (Std: Open-Circuit SCBA for Fr and Emr Srvc - Amer) {432 NFC}