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17
minute, and that this large body of air cannot go
out up the chimney unless counter-provision be made for
its entrance into the room. If provision for the entrance
of clean, warm air, to this extent into the room be not made,
the necessary air is sucked into the room through the
crevices of the doors and windows, through the cracks
in the floor, and through all the dirty crannies that are
permeable. Every house should have in its basement a constantly
open inlet for fresh air—a general-inlet with an area
sufficient to supply all the working fireplaces. The incoming
air can be filtered if necessary. But such air will
deposit most of its blacks in the basement passages, and
it loses its chill while rising up through the staircase to
supply the house. Each room should have, leading from
the staircase, an inlet over its doorway, guarded by a
louvred opening to deflect the indraught towards the ceiling
and make it travel along the upper part of the room
so as not to impinge upon the persons of the inmates. An
in-current which takes this course is ventilation ; the same
in-current, when it strikes the persons in the room, is a
draught. Raw, cold, black-laden air from the street should
not be taken into a living-room during the winter. It is
through the staircase that successful and clean ventilation
of living-rooms can best be effected ; and the motive-power
of the fire must be utilized in order to suck clean, warm
air in over the doorway, while it drives the products of
combustion up the chimney. For want of these simple
provisions ventilators do not work, or they, very naturally,
work the wrong way, and are at once pasted up.
In order to secure that each workshop, or each room of
a house, is continuously and adequately ventilated, the
following provisions must be made : —
i. The inlet over each chamber doorway should
have for its air-way a minimum cross-section of
half a square foot—i.e., 72 square inches. Its chamberface
should be furnished with a louvre so shaped
as to deflect the in-draught obliquely towards the