46. Danger of Carbon Dioxide. When carbon dioxide occurs in large
quantities, it is dangerous to health, because it interferes with
normal breathing, lessening the escape of waste matter through the
breath and preventing the access to the lungs of the oxygen necessary
for life. Carbon dioxide is not poisonous, but it cuts off the supply
of oxygen, just as water cuts it off from a drowning man.

Since every man, woman, and child constantly breathes forth carbon
dioxide, the danger in overcrowded rooms is great, and proper
ventilation is of vital importance.

47. Ventilation. In estimating the quantity of air necessary to keep
a room well aired, we must take into account the number of lights
(electric lights do not count) to be used, and the number of people to
occupy the room. The average house should provide at the _minimum_ 600
cubic feet of space for each person, and in addition, arrangements for
allowing at least 300 cubic feet of fresh air per person to enter
every hour.

In houses which have not a ventilating system, the air should be kept
fresh by intelligent action in the opening of doors and windows; and
since relatively few houses are equipped with a satisfactory system,
the following suggestions relative to intelligent ventilation are
offered.

1. Avoid drafts in ventilation.

2. Ventilate on the sheltered side of the house. If the wind is
blowing from the north, open south windows.