A carbon monoxide detector proved invaluable to occupants of a Rutland home recently, warning a woman and her daughter of unsafe levels of the invisible, odorless gas released from a furnace following a power outage.

Just after midnight on Friday, Dec. 1, a resident at a Highland Avenue home called the fire department when a detector sounded at the home, according to Lt. Gary Lambert of the Rutland City Fire Department.

With gas meters in hand, firemen found carbon monoxide just inside the front door. Immediately, they put on air packs and oxygen masks.

"We know they have had elevated levels of carbon monoxide, and out they come." Lambert said of firefighters' move to get the inhabitants out once they had determined the danger.

The level of carbon monoxide, plus smoke in the home, were high enough that the occupants already were feeling symptoms and should have already left the building, Lambert said.

Because the occupants reported feeling nauseous, firemen advised them to go the hospital to be checked, Lambert said.

Before the alarm went off, the occupants may not have known they were absorbing the gas, emitted when the furnace malfunctioned.

Based on the firemen's test at the Highland Avenue home, carbon monoxide already had reached an unsafe level, Lambert said.

In readings on their meter, firemen found 15 parts per million (ppm) at the front door — well above limit of 10 ppm on the meter.

In a reading at the top of the stairs to the basement, the carbon monoxide readings rose to 40 ppm and jumped to 53 ppm in the basement, Lambert said.

The standards applied by Rutland fire officials are very close to state Environmental Protection standards of 9 ppm of carbon monoxide over an eight-hour period used by Vermont and Maine.

The maximum one-hour concentration is set at 35 ppm, which also should not be exceeded more than once a year.

"I don't like my guys (more junior firemen) going into a place (on a fire call) at a level of seven, 8 or 9 (ppm)," said Lt. Ernie Cioffi, a shift commander with the Rutland Fire Department.

While they don't reveal precise readings, home detectors are sensitive enough to pick up trace amounts of the gas, potentially as low as 1 ppm, Cioffi said.

Just over a year ago, state officials here took steps to accept greater responsibility for the carbon monoxide threat when the Legislature enacted a law requiring the detectors in homes and apartments.

When selling a home, an owner is required by state law to provide carbon monoxide detectors in specific spots, typically near the bedrooms "prior to the conveyance of real estate," according to Kyle Kershner, a real estate agent at Ski Country Real Estate in Killington.

The seller must sign an affidavit stating there are smoke detectors in the home. "There were some catastrophic problems in the state" that brought about the law change, he said.

In recent years, the poisonous gas has been listed as the apparent cause of a number of winter deaths resulting from malfunctioning heating systems.

During exposure at less than 50 ppm, generally there may be limited adverse symptoms, according to Kevin Doering, environmental health chief, in the Vermont Health Department, while referring to the CDC standard. In the 100s ppm, the doses can be lethal, however.

As part of their training, firemen become familiar with why carbon monoxide can be such a threat.

"Carbon monoxide will impregnate the air completely," Lambert said. "Because of the make-up of carbon monoxide, it bonds to (the hemoglobin) in the red blood cells and carries through the body rapidly.''

Part of Cioffi's training as an emergency paramedic involved learning in detail how the gas is absorbed in the body, much more prone to take in carbon dioxide than the oxygen the body really wants.

Absorption of the harmful gas in the lung occurs in the alveoli, tiny capillary-rich sacs in the breathing organ where, under normal conditions, the exchange of oxygen and carbon dioxide takes place, he said.

Now, as the heating season begins to kick in full bore, city fire officials say there is a growing concern for potential carbon monoxide problems — often in older homes, Lambert said.

With the price of fuel oil staying relatively high, people will sometime overheat units not designed to heat homes, he said.

"We have seen people using heaters on stoves" to supplement their heat, he said. "Unfortunately, people get really inventive in trying to stay warm.''

The problems can stem from renewed use wood stoves and old fireplaces that have not been providing heat, Lambert said. Any unit that burns a fuel — wood, oil, natural gas or coal — gives off carbon monoxide.

Within a home, central heating systems are not the only mechanisms that can leak carbon monoxide. Early in the fall, fire officials responded to an incident where case of a gas-powered water heating unit malfunctioned and burped carbon monoxide into the home, Lambert said.

According to a recent report from the Indoor Air Quality Association, the threat also exists in new homes. In newer homes, poisoning from carbon monoxide has risen due to building improvements that have reduced the amount of air moving through a building.

According to the indoor air quality Web site, carbon monoxide kills more than 1,500 people nationwide each year and injures another 10,000.

Ensuring your furnace is property tuned, cleaned and vented are the best ways to make sure its emissions are being handled safe, Rutland city fire officials said.

Contact Tom Mitchell at tom.mitchell@rutlandherald.com.