An egress window is one which is large enough to allow a person to escape in an emergency, and to allow a fully outfitted firefighter with an oxygen tank to enter. In the past, building codes did not regulate the size and location of windows within homes. As a result, many bedrooms, especially in the basement areas, were potential fire traps if access to the stairs and doorway was blocked. Eventually, local building codes in many jurisdictions were modified to include an egress window code.

Building codes are generally legislated at the local level, and the size and type of egress required may vary between jurisdictions. In an effort to provide consistency for manufactures, however, an international residential code (IRC) has been developed which sets safety standards for construction, including specifications for egress windows. Since then, most areas in the United States, Canada and many other nations have adopted the IRC specifications for an egress window code.

The IRC specifications require that one window in each sleeping room located in the basement and up to the fourth story meet egress window code specifications. Egress windows are required to have a minimum width opening of 20 inches (50.8 cm), a minimum height of 24 inches (61 cm), and a minimum net clear opening of 5.7 square feet (.053 square m) for anything besides ground level rooms. Ground level bedrooms are only required to have a clear opening of 5 sq. feet (.046 sq. m) because no extra clearance is needed for a ladder. Additionally, egress window sills can be no more than 44 inches (1.12 m) from the floor.

For basement windows, there are also codes for egress window wells. The wells must provide 9 sq. feet (.84 sq m) of floor space, and must have a minimum of 36 inches (.091 m) in both width and height. If the well is taller than 44 inches (1.12 m) then it must include steps or a permanently fixed ladder. If a ladder is used, the steps must be 12 inches (30.48 cm) wide and not extend more than 3 inches (7.62 cm) above the top of the window well.

There are a variety of window styles which can be constructed to meet egress window code. Casement windows are side-hinged and take up the least amount of wall space. If a double hung window is used, then it must be at least 4 feet 9 inches (1.45 m) in height to meet egress window code requirements, since one-half of the window area is still blocked when this style of window is fully open. A gliding window, which slides open horizontally, must be a minimum of 4 feet (1.22 m) wide and 4 feet high (1.22 m) to meet code. Certain skylights can also be used as egress windows as long as they are no more than 44 inches (1.12 m) from the floor.

The presence of an egress window is useless if it is blocked by exterior bars, grills or grates. To meet egress window code, only bars and grills which can be easily opened or removed from the inside, without the use of a key or other tool, may be installed, Another requirement of the code is that the egress window must open to an outside area which allows a person to get safely away from the structure in the case of a fire or other emergency.

In districts which have adopted building codes, new construction is required to comply with the egress window code. Most areas, however, do not address windows in existing houses unless permits are drawn for remodeling. Some mortgage programs, such as FHA loans in the US, do require egress windows in all bedrooms regardless of the age of construction. Whether required or not, compliance with the egress window code is a prudent safety measure.