If you don’t already have at least one carbon monoxide detector in your home, add the item to your shopping list.

As of Feb. 22, nearly every private residence in New York state — single-family home, condo, duplex, multi-unit apartment house — will be subject to Amanda’s Law, approved last year in the wake of an area teen’s death from carbon monoxide poisoning.

Sixteen-year-old Amanda Hansen of West Seneca died at a friend’s house during a sleepover in January 2009. A defective boiler inside the house caused build-up of carbon monoxide, an odorless, tasteless, invisible gas that, in higher concentrations, cuts off oxygen supply to the body.

State law already required many housing units — singles built or sold later than July 2002 and multis built or sold later than August 2005 — to have carbon monoxide alarms. Amanda’s Law applies the rule retroactively, to all housing, regardless of age, wherever a carbon monoxide source is present.

Fossil fuel-fired appliances and devices — natural gas furnace/water heater, kerosene heater, woodburning fireplace, even a vehicle running inside an attached garage — are CO sources. Electric-fired devices are not.

Within single- and double-family structures, Amanda’s Law requires one CO alarm be placed on the lowest floor level where sleeping quarters are present. Within structures holding three or more units, an alarm must also be placed at basement level, where multiple/separated utilities increase chances for CO leaks.

Realistically, area building/fire code enforcers say, two or more CO alarms should be installed in homes of all types: at the floor level where an enclosed garage is attached; at all floor levels containing bedrooms; and in the basement.

Amanda’s Law requires basement-level alarm placement in multi-family homes only, but it’s good practice in all living quarters, suggested Jason Dool, chief building inspector for the City of Lockport.

“If you’re going to have a problem, it’s most likely going to start (in the basement), where the utilities are,” he said.

In 2009, fire companies responded to about 350 CO alarm activations across Niagara County, according to area fire chiefs. Results vary by fire district, but on average, investigation turns up elevated CO levels in about one-third of all incidents, they said.

Volunteer fire companies responded to 82 CO alarm calls last year; ambulances were sent automatically on 12 of them. That doesn’t mean there were 12 confirmed instances of CO elevation, county Fire Coordinator Jim Volkosh said, but ambulances were sent because at the time of the call, someone in the home reported nausea or flu-like symptoms. These are signs of CO poisoning.

North Tonawanda Fire Department took 44 calls and confirmed eight instances of CO elevation, Chief Joseph L. Krantz said.

Enforcement of Amanda’s Law will not be easy, code enforcement officers acknowledge. Rental houses are subject to mandatory inspection, but older single-family homes are not, unless work is being done that requires a building permit. No municipality has the staff to go house-to-house checking for CO detectors in any case.

Unless inspectors have cause to peer inside living units, the law will work “in a backward kind of way, like the seat-belt law,” Volkosh said. “If something happens and you weren’t wearing one you’d get in trouble. ... The onus really is on the homeowner. The cost of a carbon monoxide detector is pretty cheap insurance. You’d hope people realize what they’re protecting.”

Alarm models on the market range from the $20 battery-operated CO detector, to combination smoke/CO alarms, to high-end electronic models that display parts-per-million CO readings. “Hard wired” (electric-powered) alarms are required in newer homes, but battery-operated models are sufficient under the terms of Amanda’s Law.

Any county resident can call the Office of Emergency Management Services, 438-3171, for more information about CO issues.