There's a danger lurking in many Wisconsin homes, serious enough for the state Legislature to pass a law.
This assailant often strikes its victims as they sleep, sickening hundreds in Wisconsin each year.
"What makes carbon monoxide so dangerous is the fact that it's colorless, tasteless and odorless," Milwaukee Fire Department Deputy Chief Randall Zingler said. "You can't see it, feel it or hear it, and if it's there when you go to sleep, you might not wake up."
Beginning Tuesday, a new state law takes effect requiring carbon monoxide, or CO, alarms to be installed in all one- and two-family dwellings, according to the state Department of Health Services.
The detectors work like smoke alarms, alerting the dwelling's occupants to dangerously high levels of carbon monoxide.
Newly constructed homes will require detectors that are directly wired to the home's electrical service; owners of existing homes may use battery-powered, stand-alone detectors, according to the department.
State law now includes a similar requirement for multifamily dwellings as well as any public building that is used for sleeping or lodging purposes.
Carbon monoxide is a gas that can be emitted from poorly functioning or unvented furnaces or other gas-powered home appliances.
Outdoor appliances such as portable generators, heaters and stoves also can create dangerous levels of CO in cabins, campers, tents, and hunting and fishing shacks.
In Milwaukee, all too often outdoor appliances are used indoors by people to heat their homes when their utilities have been shut off, creating the danger of carbon monoxide poisoning, Zingler said.
Often, however, carbon monoxide leaks result from wear and tear on furnace ventilation pipes that allows the gas to escape into a home, Zingler said.
Other sources of elevated CO in homes include clogged chimneys and gas kitchen stoves that are used as a source of heat, he said.
There also have been reported instances of carbon monoxide from vehicle engines seeping into homes from attached garages.
"CO is basically caused by incomplete combustion of fossil fuels," Zingler said.
Older homes are more susceptible to carbon monoxide leaks, he said.
State health officials recommend that the detectors be installed on every level of a home and near sleeping areas. Zingler also recommends they be placed as high as possible because carbon monoxide tends to rise when it escapes.
The Milwaukee Fire Department responded to 164 confirmed incidents of elevated levels of carbon monoxide in 2010, according to department data.
In 2009, the latest year for which such statistics are available, hospital emergency rooms in Wisconsin treated 480 patients for CO poisoning, according to the state health department.
According to data from by the U.S. Consumer Product Safety Commission released in September 2009, between 2004 and 2006, carbon monoxide poisoning deaths in the United States resulting from heating systems and gas water heaters averaged 54 a year.
Carbon monoxide alarms, some of which come with smoke detectors, are relatively inexpensive.
A First Alert plug-in CO detector with a battery backup lists for $25.97 on the Walmart website, and a combination CO/smoke detector manufactured by Kidde lists for $19.99 on the site.
The devices are available at many other retail outlets, Zingler said.
Another reason carbon monoxide is potentially so dangerous is the symptoms of carbon monoxide poisoning - headache, fatigue, nausea, dizziness and vomiting - can be associated with common illnesses, which raises the importance of detectors in the home, Zingler said.
If a carbon monoxide alarm goes off, people should not open windows, because that makes it more difficult for responders to find the source of the leak, he said.
"Get everyone out of the house and call 911," Zingler said.
