oxygen could result in death, especially when the
person cannot be predicted accurately. For example, a
situation is complicated by loss of blood in combat or
person may be relatively unaffected one day, but highly
by shock due to pain or fear.
susceptible the next.
BETWEEN 20,000 AND 25,000 FEET.--During
It is difficult to detect hypoxia, because its victims
World War II, most military flying was done in
are seldom able to judge how seriously they are
unpressurized aircraft at altitudes of between 20,000
affected, or if they are affected at all. The unpleasant
and 25,000 feet. Most of the resulting anoxia deaths
sensations experienced in suffocation are absent in the
occurred in this altitude range. The general symptoms
case of hypoxia. Blurring of vision, slight shortness of
of drowsiness, mental confusion, dim vision, and
breath, a vague weak feeling, and a little dizziness are
dizziness occur here, as at lower altitudes, but they
the only warnings. Even these may be absent or so
come on much more quickly, allowing less opportunity
slight as to go unnoticed.
for corrective action. Consequently, under no cir-
While still conscious, the aviator may lose all sense
cumstances should aircraft ascend to these altitudes,
of time and spend the last moments of consciousness in
even for short periods, without the use of oxygen by all
some apparently meaningless activity. In such a
persons aboard. The movement of personnel in the
condition, a person is a menace to the crew as well as to
aircraft requires the constant use of walk-around
himself. Since the aviator understands that it is the
equipment. Unusual actions or failure of a crewmember
reduced air pressure at higher altitudes that determines
to respond quickly and clearly when called require
the effect on the body, dependence should be upon the
immediate investigation.
altimeter rather than sensations or judgment to
BETWEEN 25,000 AND 30,000 FEET.--
determine when oxygen is needed. The effects of
Between 25,000 and 30,000 feet, collapse, un-
hypoxia at various altitudes are discussed in the
consciousness, and death quickly follow interruption of
following paragraphs.
the oxygen supply. Mask leakage at these altitudes may
BELOW 10,000 FEET.--At or below 10,000 feet,
cause a degree of hypoxia that, although not noticed
some effects of hypoxia may be present. Generally, the
during flight, can produce considerable fatigue and
eye is the first part of the body to suffer effects of
have serious cumulative effects.
hypoxia. Even at a relatively low altitude of
ABOVE 30,000 FEET.--Above 30,000 feet,
approximately 5,000 feet, where no other effect of
unconsciousness and death strike rapidly and often
hypoxia can be detected, night vision may be affected,
without warning. At such altitudes, it is imperative that
due to mild oxygen starvation. Thus, the use of
all oxygen equipment is functioning correctly and that
supplemental oxygen on night flights above 5,000 feet
each breath is taken through a properly fitted oxygen
is required. Although hypoxia affects the eyes in the
mask. Above a pressure altitude of 35,000 feet,
daytime as well as at night, the results during the day
pressure breathing oxygen equipment is required.
are usually not as noticeable below 10,000 feet.
Q7-1. As an aircraft climbs, what effect occurs to
BETWEEN 10,000 AND 15,000 FEET.--
the volume of air?
Although efficiency may be considered impaired at
10,000 to 15,000 feet, death from oxygen starvation at
Q7-2. Unless an aviator breathes additional oxy-
these altitudes is virtually unknown. The greatest
gen, which three main systems on the body
dangers are from errors in judgment or performance
begin to fail?
due to drowsiness or mental confusion. At these
Q7-3. Above 33,000 feet to approximately 35,000
altitudes, long flights without oxygen produce
feet, oxygen equipment provides what per-
persistent drowsiness and excessive fatigue for many
centage of oxygen?
hours afterward. Frequently, persistent headaches
Q7-4. Above 43,000 feet, what requirement is the
develop soon after completion of the flight. For these
only adequate provision for the safety of an
reasons, the use of oxygen on flights above 10,000 feet
aviator?
is required. Portable oxygen systems are available for
Q7-5. Oxygen procured under MIL-0-27210 is
aircraft that do not have oxygen equipment.
required to be what minimum percent pure?
BETWEEN 15,000 AND 20,000 FEET.--Flights
Q7-6. What color is liquid oxygen?
at 15,000 to 20,000 feet, even for short periods, must
never be attempted without the use of oxygen. Collapse
Q7-7. A complete lack of oxygen is referred to by
and unconsciousness are common. Failure to use
what medical term?
7-3
