Compressed Air Work And Diving 1909
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AIR SUPPLY.
5
least 5 cub. It. per man per minute, measured at the
cxisting pressure, or 300 cub. ft. per man per hour.
I his larger air supply is to allow for fumes gene-
rated by blasting and other impurities; but if these
niipurities are at all excessive, a larger air supply will
be needed.
Table I. For Diving.— 1 his table has been arranged
with exposures sufficiently short to keep the time, which
must be spent in decompression, within reasonable limits.
As an example of its use we may take the case of a
diver who is going to do some work at a depth of 96 ft.
He would descend as rapidly as possible to the bottom,
taking say two minutes in doing so. At the end of
55 ~ 2 = 53 minutes at the bottom, or fifty-five minutes
from the surface, he would start coming up, and would
do so quickly (the ears can always follow any rate of
decompression), until he reached a depth of 30 ft., when
he would stop three minutes. At the end of three
minutes he would ascend to 20 ft., and stop there ten
minutes, and at the end of the ten minutes he would
ascend to a depth of 10 ft. and stop there fifteen minutes.
He would then ascend the remainder of the way to the
sur face. I he time taken in ascending to the first stopping
place might be about two minutes, and a half minute or
so for each 10 ft. of ascent between the stoppages and
the last 10 ft. He should move his arms and legs
during each stoppage in order to hasten desaturation.
1 he stoppages are regulated by signal from surface
according to the readings of the pressure gauge.
A diver has sometimes to descend twice or oftener
at short intervals. When this happens the more slowly
desaturating parts of his body will not have become de-
saturated at the time the seconcl descent begins. To
nicet the inereased risk the two periods at the bottom