Many Utahns have fired up their furnaces in recent days to cope with the recent cold snap. Although warmer weather is on the way, the recent chill in the air tells us that winter soon will be upon us and the furnace will be pressed into service day and night.

Utahns are reminded to have their furnaces checked annually to ensure they operate as safely and efficiently as possible. The experience of some condominium residents on the Salt Lake Avenues is instructive. One man was hospitalized and six others evacuated Sunday night after firefighters detected high levels of carbon monoxide. Carbon monoxide levels eight times safe limits were detected in some condominium units. Published reports said a malfunctioning furnace may have been to blame.

Homeowners and renters alike should purchase carbon monoxide detectors to provide early warning of accumulations of the potentially deadly gas. In 2000, invisible, colorless, odorless gas killed 400 people, 300 of them in residences. The risk of unintentional death from carbon monoxide poisoning is highest for people age 75 and older, according to the National Fire Protection Association, or NFPA.

The symptoms of CO poisoning are headache, dizziness, mental confusion, nausea or faintness. Unfortunately, these symptoms may be mistaken for the flu, food poisoning or other maladies. So anyone who suspects CO poisoning should seek medical attention as soon as possible.

Most people consider their furnace as the greatest threat for carbon monoxide poisoning. The NFPA Web site cautions that heating and cooking equipment that burns fuel also is a potential source of the deadly gas. The same goes for vehicles or generators that run in an attached garage.

The association also recommends that homeowners have fireplaces, water heaters, wood and coal burning stoves and chimneys inspected annually.

When a fire is lighted in a fireplace, the flue should be open to permit adequate ventilation. If a kerosene or gas heater is required, a window should be opened slightly.

A homeowner or tenant's safest course it to install a carbon monoxide detector in a low outlet because CO is heavier than air. That and strict adherence to a home-maintenance schedule should provide adequate protection from a killer that can't be detected by smell or sight.