Emergency Escape and Rescue Openings | CRC § R310


Emergency escape and rescue openings in residential dwellings are critical safety measures that enable inhabitants to quickly and safely exit a building in the event of an emergency.

To make sense of these codes, let's break down some of the technical language and key terms used:

  1. Dwelling Unit: This refers to a residential accommodation which contains living facilities, such as sleeping space, a place to prepare food, and a bathroom. In the CRC it is defined as "Any building that contains one or two dwelling units used, intended, or designed to be built, used, rented, leased, let or hired out to be occupied, or that are occupied for living purposes."
  2. Public Way: This term is generally used to describe spaces that are open for public use, like streets or alleys. In the context of these codes, it refers to a clear and unobstructed path leading away from the building to a safe space outdoors. In the CRC it is defined as "Any street, alley or other parcel of land open to the outside air leading to a public street, that has been deeded, dedicated or otherwise permanently appropriated to the public for public use and that has a clear width and height of not less than 10 feet."
  3. Net Clear Opening: This is the actual free and unobstructed space that is available when the window or door is open. In other words, it's the space through which a person could pass in case of an emergency.
  4. Operational Constraint: This refers to restrictions on how a system or mechanism can be used. For example, in the context of these codes, the operational constraint of an emergency escape and rescue opening would be that it should be easily operable from inside without requiring keys, tools, or special knowledge.
  5. ASTM F2090: This refers to a standard set by ASTM International (formerly known as American Society for Testing and Materials), a globally recognized leader in the development of standards. ASTM F2090 specifically pertains to window fall prevention devices with emergency escape (egress) and rescue capabilities.

The code sections you'll be reading are all about providing safe and accessible ways for occupants to exit a building during an emergency.  


The requirements for these openings are found in California Residential Code (CRC) R310 and California Building Code (CBC) 1031. According to the CRC, emergency escape and rescue openings must be provided in each sleeping room of a dwelling unit and in basements with habitable spaces. 

Location Requirements

Emergency escape and rescue openings shall open directly into a public way and have the bottom of the clear opening not greater than 44” measured from the floor. When installed under decks, porches and cantilevers they shall be fully openable and provide a path not less than 36” in height and 36” in width to a yard or court.

Size Requirement

The minimum net clear opening for emergency escape and rescue openings is 5.7ft2. Additionally, the minimum net clear opening height is 24” and the minimum net clear opening width is 20”. This window shall meet all three of these requirements (area, width, and height) and it’s net clear opening shall be measured from the normal operation of the opening.


  1. A net clear opening of 5ft2 is allowed for windows located such that the bottom of the clear opening is not more than 44” above or below the finished ground level adjacent to the opening. Note that the minimum width and height requirements still apply.

Operational Constraint

Emergency escape and rescue openings shall be maintained free of any obstructions and shall be operational from the inside of the room without the use of keys, tools or special knowledge. Window opening control devices and fall prevention devices complying with ASTM F2090 shall be permitted for use on windows serving as a required emergency escape and rescue opening and shall be not more than 70” above the finished floor. The release mechanism shall be maintained operable at all times.