Because so many fire deaths occur as a result of occupants of
residential buildings being asleep during a fire, the IRC
requires all sleeping rooms have windows or doors that may be
used for emergency escape or rescue. The requirement for
emergency escape and egress openings in sleeping rooms exists
because a fire will usually have spread before the occupants
are aware of the problem, and the normal exit channels may be
Openings required for emergency escape or rescue must be
located on the exterior of the building so that rescue can be
performed from the exterior. Alternatively, occupants may
escape from that opening to the exterior of the building without
having to travel through the building itself. Therefore, where
openings are required, they should open directly into a public
street, public alley, yard, or court. After the occupants pass
through the emergency escape and rescue opening, their
continued egress is essential.
The dimensions prescribed in the code for exterior wall openings
used for emergency egress and rescue, are based in part of
extensive testing by the San Diego Building and Fire Departments
to determine the proper relationships of the height and width of
window openings to adequately serve for both rescue and escape.
The minimum of 20 inches for the width is base on two criteria:
the width necessary to place a ladder within the window opening
and the width necessary to admit a fire fighter with full rescue
equipment. The minimum 24-inch height is based on the minimum
size necessary to admit a fire fighter with full rescue
equipment. By requiring a minimum net clear opening size of the
least 5.7 square feet, the code provides for an opening of
adequate dimensions. Where the opening occurs at grade level,
the opening need be only 5 square feet due to the increased ease
of access from the exterior.
In order to be accessible from the interior of the sleeping
room, the emergency escape and rescue opening cannot be located
more than 44 inches above the floor. The measurement is to be
taken from the floor to the bottom of the clear opening.
As stated in the code, the openings used for emergency escape or
rescue must be operational from the inside of the room. Where a
window is used as the emergency escape and rescue opening, it
must be a usual double-hung, horizontal sliding, or casement
window operated by the turn of a crank. Alternate window types
may be used provided they meet the intent of the code in regards
to opening size, normal window operation and require no keys or
tools for window operation.
(article excerpted from the IRC Code Commentary).
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