Carbon Monoxide (CO) Alarms | CRC § R315


Carbon monoxide (CO) alarms are essential in all homes to provide early warning against potentially dangerous levels of carbon monoxide, an odorless and colorless gas that can cause serious health issues or even death.

Let's break down some of the technical terms and concepts before proceeding:

  1. CO Alarm: This is a device that detects the presence of the carbon monoxide (CO) gas in order to prevent carbon monoxide poisoning.
  2. UL 2034: Underwriters Laboratories (UL) is a global safety certification company. UL 2034 refers to the specific safety standard for single and multiple station carbon monoxide alarms. This standard ensures that CO alarms operate effectively.
  3. UL 217: This is the UL safety standard for smoke alarms.
  4. Interconnection: This term refers to the linking of alarms so that if one alarm is triggered, all alarms in the dwelling will sound. This feature is important in larger homes where a CO alarm may be triggered in an area of the house distant from the occupants.

The sections of the CRC you're about to read provide regulations on the installation of carbon monoxide alarms in residential settings. This involves understanding where these alarms need to be installed, the standards they need to meet, and how they should function in the case of new construction or additions to existing structures.


The requirements for CO alarms are outlined in CRC R315 and are required for the construction of new dwellings. Where an addition is made to an existing dwelling, or a fuel-burning heater, appliance or fireplace is added to an existing dwelling, not previously required to be provided with carbon monoxide alarms, new carbon monoxide alarms shall be installed.


Carbon monoxide alarms shall be listed in accordance with UL 2034. Combination carbon monoxide and smoke alarms shall be listed in accordance with UL 217 and UL 2034.


CO alarms are required outside of each separate sleeping area in the immediate vicinity of the bedrooms, on every occupiable level of a dwelling unit (including basements), and where a fuel-burning appliance is located within a bedroom or its attached bathroom, a carbon monoxide alarm shall be installed within the bedroom.


For new construction of dwellings, the CO alarms shall be interconnected in such a manner that the activation of one alarm will activate all the alarms in the individual unit. For alterations to existing dwellings, interconnection of alarms is not required.