Experience indicates that fires in pure oxygen atmospheres, even at low
pressures (e.g., 1/3 atm), are extremely difficult to extinguish. While
this phenomenon has nothing to do with respiratory physiology, the risk
on flights of long duration may be so serious as to demand special
measures. Unless effective countermeasures can be devised, this risk may
argue very strongly against the use of such atmospheres in the future.
Further experimental investigation is required.