It is one of the bitter ironies of our modern age that the increasing number of practices and products we use to make our lives more comfortable often pose a potential risk to our basic health and safety.

Carbon monoxide (CO) poisoning is perhaps one of the most graphic examples. During the past decades, we have gone to outstanding lengths to winterize our homes and offices: increasing energy and heating efficiency by installing high efficiency furnaces and storm windows. Every crack is promptly caulked, every draft eliminated. Unfortunately, while making our dwellings cozier, we are also making it difficult for fresh air to enter and for carbon monoxide and other noxious compounds to be vented properly.

In fact, carbon monoxide is one of the leading causes of poisoning deaths in the United States, claiming approximately 250 lives accidentally each year, while also posing a serious health threat for many thousands of individuals and families.

One of the most dangerous aspects of carbon monoxide is that it is not ordinarily detected by our senses. As a colorless, tasteless, and odorless gas, its poisonous effect on the human body is silent and subtle. It can happen in minutes, as is often the case with automobile-related poisonings, or can take many hours. Its effects are often misdiagnosed or even overlooked, and some people have been known to suffer from poisoning continuously for months.

Poisoning begins as easily as breathing. With each breath, carbon monoxide enters the lungs where it then bonds with the hemoglobin in the bloodstream 200 times more tightly than oxygen, thereby displacing the vital oxygen normally transported by the hemoglobin to cells throughout the body. In addition, a toxic compound known as carboxyhemoglobin is formed which causes symptoms similar to the flu or food poisoning.

Confusing CO poisoning with the flu is the main reason most people do not realize that they are being poisoned at all, especially during the winter, since headaches, dizziness, fatigue, and nausea are all pretty much an accepted part of flu season. Many individuals pop a few aspirin and put up with the symptoms for months, which generally seem to disappear once Spring and warmer weather arrives.

More severe concentrations of carbon monoxide in the blood can lead to vomiting, unconsciousness, permanent neurological damage, and even death. And while everyone is at risk, of special concern are infants, children, senior citizens, and individuals with respiratory problems.

Carbon monoxide is the by-product of the incomplete combustion of any fuel source, whether natural gas, wood, charcoal, oil, kerosene, propane, or gasoline, and can be produced by a wide array of common appliances, including furnaces and water heaters, clothes dryers, space heaters, ranges and ovens, fireplaces, wood stoves, charcoal grills, and garaged automobiles.

To prevent poisoning, it is crucial that appliances be properly maintained and adjusted. Typically, a well-adjusted gas stove will give off minute amounts of carbon monoxide; but without periodic maintenance, that same stove could emit dangerously high levels of carbon monoxide. A simple check for many stoves and other appliances is the "flame test." Pilot or ignition lights and burners should be blue in color, indicating sufficient oxygen and complete combustion of the fuel source; a yellow flame indicates that combustion is incomplete due to improper supply of oxygen or a bad mix of fuel and air, resulting in higher levels of carbon monoxide.

"Venting" is also an important part of pre-venting. Appliances like gas dryers should be vented to the outside, along with non-electric space heaters. When a space heater is moved around too often to provide venting, a window should be partially opened to provide a fresh source of combustion air. And you should regularly inspect vents, flue pipes, chimneys, filters, and venting systems for all appliances, furnaces, and water heaters, checking for blockages, corrosion, cracks, or other damage. Most homeowners find it appropriate to schedule a yearly inspection by a licensed technician or contractor, with that visit including maintenance and adjustment of appliances.

One potential problem for the newer, more tightly constructed homes is backdrafting, where insufficient fresh air is admitted to a home to replace that being burned by a fireplace or wood stove. Eventually, the indoor air pressure will drop, preventing toxic exhaust gases, smoke, and fumes from escaping through vents and chimneys, even to the point where fireplace smoke is drawn back into a home with devastating consequences. It is often advisable in many of these homes to consider cracking open a window to allow pressure equalization, which will then provide safer and more efficient venting and a cleaner, complete combustion owing to a continuous and reliable fresh air supply.

A significant number of carbon monoxide poisonings occur annually as a result of automobiles being idled in a garage attached to a house. Often an individual will start a car in the morning to get it ready for a commute, will leave it running and return indoors. Even with a garage door open, a large amount of carbon monoxide can be pulled into a house, where it will continue to accumulate, potentially leading to dangerously high levels, especially when combined with other sources.

Fortunately, while we cannot see, smell, or taste carbon monoxide, it can be readily detected through two types of widely available safety devices. The cost of these CO detectors ranges from 30 to 95 dollars, and are available either as hardwire (attached to household electricity) or battery models, similar to smoke detectors. But it is important to realize that carbon monoxide and smoke detectors are exclusive units: smoke detectors cannot detect carbon monoxide, nor will a CO detector detect smoke or heat.

Some homes simply will not need a carbon monoxide detector, such as all-electric structures without combustion appliances or an attached garage. And while the risk of CO poisoning is very slight in most properly ventilated houses, townhomes, and apartments, there is a growing percentage of homeowners who believe that installing a detector is a sound investment in basic safety.

In shopping for a carbon monoxide detector, buyers are strongly urged to select a unit with the Underwriter Laboratories (UL) listing (UL 2034), which reflects a newly revised standard, effective October 1995. It is also advisable to consult a Consumer Reports study for overall ratings since there are ten detector manufacturers and at least 15 models from which to choose.

To prevent false alarms, which can range from annoying for you to expensive and, potentially, life-threatening for a fire department, never locate a detector inside or directly outside a bathroom, where high humidity can trigger a reaction, or near a furnace, fireplace, or other combustion source. Hardwired units should not be hooked up to a "switchable" circuit.

Generally, the best practice is to position a detector in a hallway outside the sleeping area of your home, and not next to a smoke detector, where the two alarms or signals might be confused.

If your detector goes off, determine whether you are receiving a smoke detector or carbon monoxide alarm. Also identify whether the CO detector is emitting a steady alarm tone or just an intermittent warning tone (chirping), indicating a lower, less serious CO concentration.

If you are receiving a warning, open several windows or doors to get fresh air inside your home, reset your detector, and check on all potential sources of carbon monoxide, turning them off, adjusting, or repairing, where necessary.

If you receive an alarm -- and if someone demonstrates symptoms such as headaches, dizziness, or nausea -- call 911 and move everyone to a place with fresh air. Do not reenter until your home is completely aired out and the problem has been corrected. If no one exhibits symptoms, turn off all combustion sources, get fresh air inside your home, reset the detector, and have a certified technician check your appliances, other combustion sources, and venting and heat exchange systems.

Additional and detailed information about carbon monoxide poison prevention and carbon monoxide detectors, including presentations to homeowner and condominium associations, is available at the Department of Environmental Protection, phone: 240.777.7770 or email.

DEP also produces the publication Carbon Monoxide -- What You Should Know, and can make available the EPA/Consumer Product Safety Commission publication The Inside Story: A Guide to Indoor Air Quality at the same number. Additional assistance can be found by calling:

• Environmental Health Information Center: 301.929.5520
• Washington Gas: 703.750.1000
• Underwriters Laboratories: 708.272.8800, ext. 43436