BRK Carbon Monoxide Detectors are all Listed to Underwriters Laboratories Safety Standard 2034 for residential carbon monoxide alarms. Designed to warn of toxic CO gas - the leading cause of death by poisoning in the U.S. Throughout the country, municipalities are coding in CO alarms. In addition, many home builders are now offering carbon monoxide alarms as an option to new home buyers. The full line includes 120 VAC wired-in, 9V DC/battery operated and 120 VAC plug-in models. Choose the model that meets the needs of your particular installation!