The normal quantity of this gas contained in the air we breathe
is 0.04; one per cent, of it causes distress in breathing; two per cent,
is dangerous; four per cent, extinguishes life, and four per cent of it
is contained in air expelled from the lungs. According to Dr. Tidy's
table, each ordinary jet of common gas contributes to the air of a room
sixteen by ten feet on the sides and nine feet high, containing 1,440
cubic feet of air, twenty-two per cent, of carbonic acid gas, which,
continued for twenty-four hours without ventilation, would reach the
fatal four per cent.
Prof. Huxley gives, as a result of chemical analyses, the following
table of ratio of carbonic-acid gas in the atmosphere at the points
named:
On the Thames, at London 0.0343
In the streets of London 0.0380
Top of Ben Nevis 0.0327
Dress circle of Haymarket theater (11:30 P.M.) 0.0757
Chancery Court (seven feet from the ground) 0.1930
From working mines (average of 339 samples) 0.7853
Largest amount in a Cornish mine 2.0500
In addition to the consumption of oxygen and production of carbonic acid
by the use of common gas, the gas itself, owing to defectiveness of the
burner, is projected into the air.
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