By Jay Romano

New York Times News Service

Earlier this month, six residents in a New York apartment building–three of them children–narrowly escaped death when paramedics responding to a call determined that there was carbon monoxide in the building.

Also, carbon monoxide from gas-burning furnaces filled two houses this month–one on Long Island, N.Y., and one in East Lyme, Conn. Although the residents of the Long Island home survived, three people in the Connecticut home died.And last week two members of a New York family died of carbon monoxide poisoning caused by a suspected leak in a gas boiler ventilation pipe.

According to Underwriters Laboratories, the product-testing organization based in Northbrook, more than 500 people in the United States are killed each year in carbon-monoxide-related incidents. Of that number, more than 200 are killed by carbon monoxide emitted from a consumer product like a stove or water heater.Another 10,000 seek medical attention after accidental carbon monoxide poisoning.

“You can’t hear, taste, see or smell it,” said Paul Patty, Underwriters Laboratories’ resident expert on carbon monoxide. “It’s nicknamed the `silent killer’ because it sneaks up on its victims and can take lives without warning.”

Carbon monoxide (chemical symbol, CO) is a byproduct of incomplete combustion, Patty said. Sources of CO include malfunctioning appliances, such as furnaces and stoves that burn fossil fuels like natural gas or propane. Other sources include vehicle exhaust, blocked chimney flues and gas or charcoal grills that are used in the home or in an unventilated tent, camper or garage.

Patty said the initial signs of carbon monoxide poisoning are flu-like symptoms, including nausea, fatigue, headaches, dizziness, confusion and difficulty breathing. “Because CO poisoning often causes a victim’s blood pressure to rise, the victim’s skin may take on a pink or red cast,” he said. “Young children and household pets are typically the first affected.”

Fortunately, relatively inexpensive devices can detect harmful levels of carbon monoxide even before the symptoms of CO poisoning are felt.

Ken Giles, a spokesman for the Consumer Product Safety Commission in Washington, said that while early versions of carbon monoxide alarms were somewhat unreliable–some would detect atmospheric carbon monoxide and trigger a false alarm–alarms on the market today recognize carbon monoxide from a fuel-burning appliance in the home and then trigger an alarm before CO levels become dangerous.

“A carbon monoxide alarm today is triggered by a combination of the amount of carbon monoxide and the duration of its presence,” Giles said. For example, he said, a carbon monoxide alarm should sound when it detects 30 parts per million of CO for 30 days; 70 parts per million for 180 minutes; 150 parts per million for 50 minutes; and 400 parts per million for 15 minutes.

There are three different technologies used in CO detectors: biomimetic, metal oxide semiconductor and electrochemical.

Biomimetic detectors use chemicals that darken when carbon monoxide is present, blocking an internal light source from reaching a receiver and sounding the alarm.Although biomimetic technology is still used, such detectors are sensitive to temperature and humidity and are not as precise as newer technologies.

With a metal oxide semiconductor detector carbon monoxide is detected through the periodic heating of a chemical in the unit to 300 degrees Celsius. While such detectors are accurate, they are typically “hard wired” to the home’s electrical system. The most advanced technology today is electrochemical, which uses platinum electrodes imbedded in an electrolyte solution to form a sensor. Such units are precise and battery-operated and can provide instantaneous monitoring of carbon monoxide at even very low levels.

One big problem with carbon monoxide detectors is that none last indefinitely. The sensor degrades. Carbon monoxide detectors should be replaced at least once every five years. Lauren Hackett, a spokeswoman for Consumers Union–the company based in Yonkers, N.Y., that publishes Consumer Reports–said that while most carbon monoxide detectors have a test button, pushing it generally means that you are checking the electrical circuits, not that the sensor is responding to the presence of CO.

She said all homes should have at least one carbon monoxide detector but ideally alarms should be installed on each level.