Avoiding Carbon Monoxide Hazards
Safe Home Heating
It's so easy and automatic that people just don't think about it. Every year, when the weather turns cold, homeowners reach for household thermostats, flip a switch to turn on the heat and set the temperature to 68 or 70 degrees. Little thought is given to whether the furnace exhaust system—the chimney and connector pipe—is ready to provide safe, effective service.
Consumer confidence in the convenience and safety of today's home heating systems is usually well-placed. The oil and gas heating industries have achieved impressive safety records. Nonetheless, over 200 people across the nation are known to die each year from carbon monoxide poisoning caused by problems in the venting—out of their homes—of toxic gases produced by their heating systems. This is according to statistics compiled by the U.S. Consumer Product Safety Commission. Other agencies estimate actual numbers at between 2,000 and 4,000.
In addition, around 10,000 cases of carbon monoxide-related "injuries" are diagnosed each year. Because the symptoms of prolonged, low-level carbon monoxide poisoning "mimic" the symptoms of common winter ailments (headaches, nausea, dizziness, fatigue, and even seasonal depression), many cases are not detected until permanent, subtle damage to the brain, heart and other organs and tissues has occurred. The difficulty of diagnosis also means the numbers of people affected may be even higher.
Fortunately, regular chimney system inspection and maintenance can prevent poisoning incidents like these.
What Carbon Monoxide Does to You
Too much carbon monoxide in your blood will kill you. Most of us know to try to avoid this. Less well known is the fact that low-level exposure to this gas also endangers your health.
One of the truths of our human bodies is that, given a choice between carbon monoxide and oxygen, the protein hemoglobin in our blood will always latch on to carbon monoxide and ignore the life-giving oxygen. Because of this natural chemical affinity, our bodies—in effect—replace oxygen with carbon monoxide in our bloodstream, causing greater or lesser levels of cell suffocation depending on the intensity and duration of exposure.
The side-effects that can result from this low-level exposure include permanent organ and brain damage. Infants and the elderly are more susceptible than healthy adults, as are those with anemia or heart disease.
The symptoms of low-level carbon monoxide poisoning are so easily mistaken for those of the common cold, flu or exhaustion, that proper diagnosis can be delayed. Because of this, be sure to see your physician about persistent, flu-like symptoms, chronic fatigue or generalized depression. If blood levels of carbon monoxide are found to be high, treatment is important.
Meanwhile, it makes good sense to put heating system inspection and maintenance on your annual get-ready-for winter list. Prevention is the best cure.
Causes of Heating System Problems
Why is poisoning from carbon monoxide on the rise? And why does it stem primarily from home heating systems that at first glance can seem the same as those that have been used safely for years?
Caring for Your Chimneys & Flues
When gas and oil burn in vented heating systems—in order to produce household heat—the dangerous fumes that are by-products of combustion range from soot (particulate matter) to nitrogen dioxide (also toxic) to acidic water vapors formed when moisture condenses. None of these pollutants should be allowed to leak from the chimney into your living space.
In addition to carrying off toxic gases, chimneys also create the draft (flow of air) that provides the proper air and fuel mixture for efficient operation of the heating appliance—whether a furnace or boiler. Unfortunately, many chimneys in daily use in homes throughout the country either are improperly sized or have conditions that make them unable to perform their intended function.
Chimney Problems to Avoid
Oil and gas furnaces have distinct burning characteristics and produce different combustion by-products. However, the chimneys and connector pipes that serve them share common problems. Both systems are subject to weathering, animal invasions, deterioration and rust-out and the accumulation of nest materials and debris. Both require regular care and maintenance.
Oil flues need to be cleaned and inspected annually because deposits of soot may build up on the interior wall of the chimney liner. The amount of soot depends on how well-tuned the furnace is and whether the house provides sufficient air for combustion. Excessive soot causes problems that range from chimney fires to flue deterioration to chimney blockages that direct toxic fumes back into the house and cause inefficient furnace operation.
Natural gas is a clean-burning fuel, but today's high-efficiency gas furnaces pose a special problem. The fumes they produce are cooler and contain high levels of water vapor, which are more likely to cause condensation than older models. Since these vapors also contain chlorides picked up from house-supplied combustion air, the flues are subjected to more corrosive conditions than before.
Even worse, many gas appliances use chimneys that once served oil furnaces. If the liners of these chimneys are made of terra cotta (fired clay commonly used in chimney construction), bits and pieces of them slowly flake off under corrosive conditions. The combination of water-laden gas vapors available to mix with old oil soot deposits speeds this process, and debris that can block the chimney builds up at the bottom of the flue.
To the extent that problems with either of these heating systems interfere with the flow of toxic gases and particles out of the house, they may also force carbon monoxide, fumes and possibly soot into the living spaces of your home. They may cause a one-time, high-level exposure situation or release smaller amounts more regularly over a longer period. These problems should never be ignored.
Preventing Problems
In the United States, numerous agencies and organizations now recognize the importance of annual heating system inspection and maintenance in preventing carbon monoxide poisoning. The U.S. Consumer Product Safety Commission, the U.S. Environmental Protection Agency, the National Fire Protection Association, and the American Lung Association are some of the organizations that now encourage the regular maintenance of home heating systems and their chimneys in order to keep "the silent killer" at bay.
A well-tuned furnace or boiler—connected to a venting system or flue that is correctly-sized, structurally sound, clean and free of blockages—will operate efficiently and produce a warm and comfortable home. An overlooked heating system can produce death and heartbreak.
Considering the risks involved when gas or oil systems are neglected - and the benefits that accrue when they are properly maintained—you would do well to have your chimneys checked annually by a CSIA Certified Chimney Sweep® and swept or repaired as needed. This can keep illness or death from carbon monoxide poisoning from claiming you or those you love.
"Chimneys really decorate the roofline of a home... and they're maintenance-free, besides. Right?"
Your chimney—and the flue that lines it—adds architectural interest to your home, but its' real function is to carry dangerous flue gases from your fireplace, wood stove or furnace safely out of your home. A chimney helps your household air stay breathable, just as your windows and your bathroom, attic and kitchen vents do. Unlike those other exhaust points in your home, however, fireplace and wood stove chimneys need a special kind of care.
As you snuggle in front of a cozy fire or bask in the warmth of your wood stove, you are taking part in a ritual of comfort and enjoyment handed down through the centuries. The last thing you are likely to be thinking about is the condition of your chimney. However, if you don't give some thought to it before you light those winter fires, your enjoyment may be very short-lived. Why? Dirty chimneys can cause chimney fires, which damage structures, destroy homes and injure or kill people.
No One Welcomes a Chimney Fire
A chimney fire in action can be impressive. Indications of a chimney fire have been described as creating:
Creosote & Chimney Fires: What You Must Know
Fireplaces and wood stoves are designed to safely contain wood-fuel fires, while providing heat for a home. The chimneys that serve them have the job of expelling the by-products of combustion—the substances produced when wood burns. These include smoke, water vapor, gases, unburned wood particles, hydrocarbon, tar fog and assorted minerals. As these substances exit the fireplace or wood stove, and flow up into the relatively cooler chimney, condensation occurs. The resulting residue that sticks to the inner walls of the chimney is called creosote.
Creosote is black or brown in appearance. It can be crusty and flaky; tar-like, drippy and sticky; or shiny and hardened. Often, all forms will occur in one chimney system. Whatever form it takes, creosote is highly combustible. If it builds up in sufficient quantities—and the internal flue temperature is high enough—the result could be a chimney fire. Certain conditions encourage the buildup of creosote. Restricted air supply, unseasoned wood and, cooler than normal chimney temperatures are all factors that can accelerate the buildup of creosote on chimney flue walls. Air supply may be restricted by closing the glass doors, by failing to open the damper wide enough, and the lack of sufficient make-up air to move heated smoke up the chimney rapidly (the longer the smoke's "residence time" in the flue, the more likely is it that creosote will form). A wood stove's air supply can be limited by closing down the stove damper or air inlets too soon or too much. Burning unseasoned wood—because so much energy is used initially just to drive off the water trapped in the cells of the logs—keeps the resulting smoke cooler, than if seasoned wood is used. In the case of wood stoves, overloading the firebox with wood in an attempt to get a longer burn time also contributes to creosote buildup.
How Chimney Fires Hurt Chimneys
Masonry Chimneys: When a chimney fire occurs in a masonry chimney—whether the flue is an older, unlined type or tile lined to meet current safety codes—the high temperatures at which they burn (around 2000°F) can "melt mortar, crack tiles, cause liners to collapse and damage the outer masonry material". Most often, thermal shock occurs and tiles crack and mortar is displaced, which provides a pathway for flames to reach the combustible wood frame of the house. This event is extremely dangerous, call 911 immediately.
Pre-fabricated, factory-built, metal chimneys: To be installed in most jurisdictions in the United States, factory built, metal chimneys that are designed to vent wood burning stoves or pre-fabricated metal fireplaces must pass special tests. Most tests require the chimney to withstand flue temperatures up to 2100°F—without sustaining damage. Under chimney fire conditions, damage to these systems still may occur. When pre-fabricated, factory-built metal chimneys are damaged by a chimney fire, they should no longer be used and must be replaced.
Special Effects on Wood Stoves: Wood stoves are made to contain hot fires. The connector pipes that run from the stove to the chimney are another matter. They cannot withstand the high temperatures produced during a chimney fire and can warp, buckle and even separate from the vibrations created by air turbulence during a fire. If damaged by a chimney fire, they must be replaced.
Nine Signs that You've Had a Chimney Fire
Since a chimney, damaged by a chimney fire, can endanger a home and its' occupants and a chimney fire can occur without anyone being aware of them it's important to have your chimney regularly inspected by a CSIA Certifed Chimney Sweep. Here are the signs that a professional chimney sweep looks for:
Proper Maintenance
Clean chimneys don't catch fire. Make sure a CSIA Certified Chimney Sweep inspects your solid fuel venting system annually, and cleans and repairs it whenever needed. Your sweep may have other maintenance recommendations depending on how you use your fireplace or stove. CSIA recommends that you call on CSIA Certified Chimney Sweeps, since they are regularly tested on their understanding of the complexities of chimney and venting system.
All above information comes from the CSIA website.
