house may also be lessened by providing healthful ventilation in all
apartments wherein gas shall be consumed.

This subject of, the ventilation of rooms in which common gas is
ordinarily used is beginning to attract attention. It is stated, upon
scientific authority, that a jet of common gas, equivalent to twelve
sperm candles, consumes 5.45 cubic feet of oxygen per hour, producing
3.21 feet of carbonic acid gas, vitiating, according to Dr. Tidy's
"Handbook of Chemistry," 348.25 cubic feet of air. In every five cubic
feet of pure air in a room there is one cubic foot of oxygen and four
of nitrogen. Without oxygen human life, as well as light, would become
extinct. It is asserted that one common gas-jet consumes as much oxygen
as five persons.

Carbonic acid gas is the element which, in deep mines and vaults, causes
almost instant insensibility and suffocation to persons subjected to its
influences, and instantly extinguishes the flame of any light lowered
into it. 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: