SPRING VALLEY — Devices to warn people of potentially deadly levels of carbon monoxide are becoming as common in Rockland homes as smoke detectors because of a new county Health Department regulation.

The regulation requiring carbon monoxide detectors in homes and apartments went into effect earlier in the summer, and county housing inspectors have just started to check for the devices when visiting local residences.

That has homeowners and landlords like Bob Nixon scrambling to install carbon monoxide detectors so they comply with the law.

“It’s an added benefit for the protection of the tenants,” Nixon, manager and part owner of the Surrey Carlton, a 179-unit complex in Spring Valley, said as he installed a carbon monoxide detector in an apartment yesterday morning.

Carbon monoxide is a colorless, odorless gas produced from burning fuel.

In the home, it is formed from incomplete combustion of any flame-fueled device, including stoves, ovens, clothes dryers, furnaces, fireplaces, grills, space heaters, vehicles and water heaters.

When carbon monoxide is inhaled, it passes from the lungs into the hemoglobin molecules of red blood cells, interfering with the body’s ability to use oxygen.

A person exposed to carbon monoxide quickly becomes starved for oxygen.

The gas can be detected by relatively inexpensive devices that are easy to install.

Nixon recently bought about 200 carbon monoxide detectors for $38 each.

“Not a bad investment,” he said, as he inspected the device.

Under a law enacted last year by the Rockland County Legislature, all homes built after 2003 must have carbon monoxide detectors.

Apartment buildings, hotels and other multiple-family dwellings are required to have the devices.

But the Health Department was unable to enforce the regulation until it became part of the county’s sanitary code last month.

The regulation requires carbon monoxide detectors to be installed within 10 feet of the entrance of all bedrooms in a house, apartment, motel, hotel, rooming house or mobile home. The detectors must be either battery-powered or connected to the electrical system with a battery backup.

In addition, as of July 1, all homes have been required to have carbon monoxide detectors installed before they are sold or resold.

Many homeowners and apartment managers are surprised to learn of the regulation, said David Basnight, a housing inspector with the Rockland Department of Health.

Basnight and other housing inspectors are now educating homeowners and landlords about the regulation.

But property owners who repeatedly fail to install the devices face fines.

“Most people are complying,” he said. “Some more quickly than others.”

Cheryl Lamphier, manager of a rooming house for pregnant women and single women with newborns in Spring Valley, said she bought carbon monoxide detectors for each level of the three-story house as soon as Basnight told her about the requirement.

The home now has a detector in the basement near the furnace — a common source of the deadly gas — in the kitchen near the stove and upstairs in the hallway where bedrooms are.

She spent a little more than $100 for the three detectors.

“It’s a small price to pay, considering the benefits,” Lamphier said yesterday, as Basnight completed a routine inspection of the home.

The detectors, which emit an ear-splitting alarm when activated, have never given a false alarm, she said.

Residents of the home said they were glad the devices had been put in place.

“It’s like a smoke detector,” Stacey McIndoe said. “You don’t even notice it’s there.”

Real estate agents said they were telling clients to make sure the devices were installed before their houses went on the market.

New City real estate agent Debbie Russo said she reminded clients that they had to have a carbon monoxide detector in the home before they could close the deal to sell the property.

Sometimes, it’s left to the last minute.

Russo, who works for Joyce Realty, said that on her way to a closing recently, she had to stop at The Home Depot and buy a carbon monoxide detector.

“We couldn’t sell the house without it,” she recalled. “The law says you have to have