All openings in such walls must be provided with such fireproof doors
as will prove reliable in time of need. Experience with iron doors of
various forms of construction show that they have been utterly
unreliable in resisting the heat of even a small fire. They will warp
and buckle so as to open the passageway and allow the fire to pass
through the doorway into the next room.
A door made of wood, completely enveloped by sheets of tinned iron,
and strongly fastened to the wall, has proved to resist fire better
than any door which can be applied to general use. I have seen such
doors in division walls where they had successfully resisted the flame
which destroyed four stories of a building filled with combustible
material, without imposing any injury upon the door except the removal
of the tin on the sheet iron; and the doors were kept in further
service without any repairs other than a coat of paint.
The reason for this resistance to fire is that the wood, being a poor
conductor of heat, will not warp and buckle under heat, and cannot
burn for lack of air to support combustion. A removal of the sheet
metal on such a door after a fire in a mill shows that the surface of
the wood is carbonized, not burned, reduced to charcoal, but not to
ashes.
Many fire doors are constructed and hung in such a manner that it is
doubtful whether they could withstand a fire serious enough to require
their services.
The door should be made of two thicknesses of matched pine boards of
well dried stock, and thoroughly fastened with clinched nails. It
should be covered with heavy tin, secured by hanging strips, and the
sheets lock-jointed to each other, with the edge sheets wrapping
around, so that no seam will be left on the edge.
Sliding doors are preferable to swinging doors for many reasons,
especially because they cannot be interfered with by objects on the
floor. But, if swinging doors are used, care should be taken that the
hinges and latches are very strong, and securely fastened directly to
the walls, and not to furring or anything in turn attached to the
walls. The portion of the fixtures attached to the doors must be
fastened by carriage bolts, and not by wood screws.
Sliding on trucks is the preferable method of hanging sliding doors,
inclined two and one half inches to the foot, and bolted to the wall.
The trucks should be heavy "barn door hangers," bolted to the door;
and a grooved door jamb, of wood, covered with tin similar to the
door, should receive it when shut. A step of wood will hold the door
against the wall when closed. A threshold in the doorway retards fire
from passing under the door, and also prevents the flow of water from
one room to another.
These doors are usually placed in pairs, and sometimes an automatic
sprinkler is placed between them.
Fire doors should always be closed at night. In some well ordered
establishments there is a printed notice over each door directing the
night watchmen to close such doors after them. In a storage warehouse
in Boston, the fire doors are connected with the watchman's electric
clock system, so that all openings of fire doors are matters of record
on the dial sheet.
Fire doors should certainly be closed at times of fire; yet, that such
doors are open at night fires, or left open by fleeing help at day
fires, is an old story with underwriters. A simple automatic device
can be used to shut such doors. It consists of two round pieces of
wood with a scarfed joint held by a ferrule, forming a strut which is
placed on two pins, keeping the door open, as other sticks have long
since served like purposes.
The peculiarity of this arrangement is that the ferrule is not
homogeneous, but is made up of four segments of brass soldered
together with the alloy fusible at 163 degrees Fahr., which is widely
known for its use in automatic sprinklers. When the solder yields, the
rod cripples, and the door rolls down the inclined rail and shuts. At
any time the door can be closed by removing one end of the rod from
one of the pins and allowing it to hang from the other pin.