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 blocked.

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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