These are described in NFPA 1981. section 6.2.3, as specified in 42 CFR 84 for
a. 2007-compliant SCBAs, which created a 20%-25% activation range. However, for
b. 2013-compliant SCBAs, NFPA changed the design requirement in NFPA 1981, section
c. 6.2.6, by requiring the alarm range for low air to be a 33% minimum.