WESTPORT - A new law taking effect on Jan. 1 will change carbon monoxide detector requirements for people buying or selling a house.

Under the new state law, homes built before Oct. 1, 2005 must have carbon monoxide detectors in addition to smoke detectors. Homes built after 2005 were already required to have them.

Fire officials say the alarms are necessary because carbon monoxide is toxic. They say people should have one on every floor of their homes.

Officials say that what makes carbon monoxide extremely dangerous is that it is colorless and odorless, and residents won't know it's there until an alarm goes off or until they begin to experience medical symptoms.

Under the law, anyone selling a house without carbon monoxide detectors will have to credit the buyer $250.