September, 
I9 1 5 
HOUSE 
AND GARDEN 
23 
poisonous qualities. Nevertheless, car¬ 
bon dioxide does indicate the amount 
of respiration the air has undergone, 
and, therefore, should be considered in 
determining the degree of purity. 
Practically, pure air contains four 
parts of carbon dioxide to 10,000. Air 
exhaled from the lungs contains 400 
parts in 10,000. This exhaled air min¬ 
gles with the pure air in the room and 
thereby contaminates a quantity very 
much in excess of that actually used. 
It is, therefore, found necessary to 
supply about 100 times the quantity 
actually breathed to obtain a practical 
degree of purity. This is equivalent to 
30 cubic feet per minute or 1,800 cubic 
feet per hour, per person, which will 
give a carbon dioxide content of about 
eight or nine parts in 10,000. 
It is now seen that in a room whose 
dimensions are 14' x 14' x 9', or whose 
cubic contents are approximately 1,800 
cubic feet, the air would have to be 
completely changed once per hour if 
only one person occupied the room. If 
two people are in the room, two changes 
are necessary. Fortunately for us, few 
residences are built to exclude all air 
and certain quantities find their way 
through crevices in the walls, through 
window sashes, door frames, etc. It 
is more desirable to admit smaller quan¬ 
tities of air continuously than to admit 
large quantities at intervals. 
Even an open window may not en¬ 
sure perfect ventilation at times. We 
must have some means for moving the 
air. Nature has supplied us with a 
powerful ventilating force in the winds. 
A comparatively small opening into a 
room from the windward side of the 
house, with the wind barely perceptible, 
will, in nearly every case, supply more 
times enough air for ventilation, pro¬ 
vided it is diffused. This may easily he 
accomplished by attaching a deflecting screen to the window 
If the radiator must protrude into the room, have 
where the grill is not feasible, a piece of chintz 
it boxed in with such a grill as shown. In some instances, 
in the colors of the room can be laid over the radiator 
sill. 
If no positive system of ventilation is installed in the house, 
ventilation without drafts may be had by the use of the window 
ventilator shown on page 24. A board about eight inches wide and 
a little longer than the width of the sash should he fastened to 
the window frame at a distance from the sash. This will direct 
the air upwards and prevent a direct draft from striking the 
occupants of the room. If the board is stained to match the 
finish of the woodwork, it will not be unsightly. This same ar¬ 
rangement is sometimes worked out with a glass frame, which 
has the advantage of not excluding light. Another method in 
extensive use for moving air is by heat. A heated column of 
air will rise, and if a ventilating shaft that is neither too large nor 
too small enters the room a proper change of air will be 
accomplished. 
Another method of moving air is by mechanical means. A fan 
is used in this system to either force air into the room or to 
extract the air from the room. Such a system is expensive and 
it is not adaptable to small houses. 
It is not the purpose of this article to cover the details con- 
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