Summary
We propose to adopt a new airworthiness directive (AD) for various transport airplanes equipped with certain B/E Aerospace protective breathing equipment (PBE) units. This proposed AD would require removing affected PBE units. This proposed AD results from reports of potentially defective potassium superoxide canisters used in PBE units, which could result in an exothermic reaction and ignition. We are proposing this AD to prevent PBE units from igniting, which could result in a fire and possible injury to the flightcrew or other persons.