a. Several investigators had reported that the presence of beards
caused a decrement in the efficiency on half masks, full masks, and -.
respirators. A Department of Navy study (No. NADC-722110CS) reported an '
average inboard leakage of
16 to 67 percent for military-type crew oxygen
masks when tested with subjects wearing beards to altitudes of 18,000 feet.
Civilian crew oxygen masks vary considerably from these types of masks
because of differences in basic mask designs, suspension systems,.,and
controlling regulators. Consequently, CAMI conducted'research to determine
if the problems noted in these reports would also be present when civil
aviation oxygen equipment was tested.
.... respirator/oxygen (sometimes
referred to as "demand") masks cannot be donned rapidly and do not seal
over beards or heavy facial hair. This lack of a seal could result in a
reduced amount of oxygen in the mask and the entry of smoke or toxic fumes
that could result in
reduced crewmember capability and performance.
...This can adversely affect the performance of the mask and reduce crewmember
awareness, capability, and performance.
http://www.airweb.faa.gov/Regulatory...E/AC120-43.pdf