OXYGEN
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Oxygen is a very toxic gas and an extreme fire hazard. It is fatal in
concentrations of as little as 0.000001 p.p.m. Humans exposed to these oxygen
concentrations die within a few minutes. Symptoms resemble very much those of
cyanide poisoning (blue face, etc.) In higher concentration e.g. about 20%,
the toxic effect is somewhat delayed and it takes about 2.5 billion
inhalations before death takes place. The reason for the delay is the
difference in mechanism of the toxic effect of of oxygen in 20% concentration.
It apparently contributes to a complex process called aging, of which very
little is known, except that it is always fatal.

However, the main disadvantage of the 20% oxygen concentration is the fact
that it is habit forming. The first inhalation (occurring at birth) is
sufficient to make oxygen addiction permanent. After that, any considerable
decrease in the daily oxygen doses results in death with symptoms resembling
those of cyanide poisoning.

Concentrations higher than 20% decrease the above mentioned delay. High
oxygen concentration provokes in prematurely born babies placed in incubators
a condition known as retrolental fibroplasia resulting in blindness. Lung
irritation has been reported on experimental animals exposed for several days
to high oxygen concentrations.

Oxygen is an extreme fire hazard. All the fires that were reported in the
continental U.S. for the period of the past 25 years were found to be due to
the presence of this gas in the atmosphere surrounding the buildings in
question.

Oxygen is especially dangerous because it is odorless, colorless and
tasteless, so that its presence cannot be readily detected until it is too
late.