Frequently Asked Questions
When gas and oil burn in vented heating systems, the dangerous fumes that are the by-products of combustion – including carbon
monoxide – are released into the chimney through a connector pipe. Funneling these fumes out of the living area is the primary purpose
of a chimney. 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. 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.
Natural gas is a clean-burning fuel, but todays high-efficiency gas furnaces pose special problems. (see the pages on GAS for a more
complete discussion) The fumes they produce are cooler and contain high levels of water vapor, which cause more 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 and can quickly deteriorate or plug up completely.
Oil flues need to be cleaned and inspected annually because deposits of soot may build up on the interior walls of the chimney. 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 ranging from inefficient furnace operation to completely blocked chimneys.
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 into the 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.
This has become quite a common problem in modern air tight houses where weather proofing has sealed up the usual air infiltration
routes. The fireplace in use exhausts household air until a negative pressure situation exists. If the house is fairly tight, the simplest route
for makeup air to enter the structure is often the unused fireplace chimney. As air is drawn down this unused flue, it picks up smoke that
is exiting nearby from the fireplace in use and delivers the smoke to the living area. The best solution is to provide makeup air to the
house so the negative pressure problem no longer exists, thus eliminating not only the smoke problem, but also the potential for carbon
monoxide to be drawn back down the furnace chimney. A secondary solution is to install a top mount damper on the fireplace that is used
The smell is due to creosote deposits in the chimney, a natural byproduct of wood burning. The odor is usually worse in the summer when
the humidity is high and the air conditioner is turned on. A good cleaning will help but usually won’t solve the problem completely. There
are commercial chimney deodorants that work pretty well, and many people have good results with baking soda or even kitty litter set in
the fireplace. The real problem is the air being drawn down the chimney, a symptom of overall pressure problems in the house. Some
make-up air should be introduced somewhere else in the house. A tight sealing, top mounted damper will also reduce this air flow coming
down the chimney.
There are a multitude of reasons for smokey fireplaces . We have included an entire section on smoking fireplaces in the fireplace area
and we suggest you go there for a better discussion of this problem.
Without a doubt! Although gas is generally a clean burning fuel, the chimney can become non-functional from bird nests or other debris
blocking the flue. Modern furnaces can also cause many problems with the average flues intended to vent the older generation of
Your past experiences with chimney sweeps sound as though the sweep did the job he was hired to do. However, your most recent
experience sounds a bit odd. If the sweep agreed to do a complete sweeping and only cleaned the brick in the fireplace firebox, you did
not get the service that you paid for. A complete chimney sweeping includes the chimney flue and smoke chamber. In the future, you
could ask for a Level 1 chimney inspection and a chimney sweeping. If the sweep doesn’t know what a Level 1 inspection is, find one that
does. A Level 1 inspection is detailed in the National Fire Protection Association 211: Standard on Chimneys, Fireplaces, Vents and Solid
In the past, sweeps we’ve hired have always gone on the roof, checked the flashing, the mortar and all the workings of the chimney and
then cleaned the chimney from the top of the house. Today, this sweep came in, looked into my fireplace from the bottom and said we
don’t need it clean because he can still see the bricks. My asked to have it cleaned anyway. He then grabbed a wire brush and simply
rubbed away any buildup from the main opening to the fireplace without even going up into the chimney to clean anything.
here may be weaknesses in the bricks and mortar. The fireclay lining could be cracked. Even worse, many chimneys have no lining at
all. Most old chimneys do not provide suitable venting for new wood appliances. These old chimneys need to be retrofitted with new liners.
If not, the results could be disastrous. If you own a wood heating system, have a certified chimney professional inspect, clean, and
replace any necessary parts.
Without any visible signs, acid produced by your gas appliance may be eating away at the inside of your chimney, putting your family at
risk. Regular inspections of your chimney can alert you to potential problems before they become costly or dangerous. Chimney
evaluations are especially important when older chimneys are paired with higher-efficiency appliances and boilers. Improper matches
often occur when flues or the connector pipes are too large. With improper matches, a blockage can occur that could prevent carbon
monoxide from leaving the system and allow it to enter your home. Improper matches can also cause inadequate draft in the system. This
can reduce the efficiency and safety of the appliance. Evaluations are recommended for newer chimneys as well. Make sure that your
furnace was installed according to the manufacturer’s installation instructions and the NFPS standards.
With oil appliances, soot accumulation can restrict the flow of nitrogen, carbon dioxide and water vapor and not allow CO2 to be properly
vented. This which could result in the CO2 spilling back into the house instead of going up the chimney. Also, a chimney’s interior, if not
properly maintained will decay and break down.
This a tougher question than it sounds. The simple answer is: The National Fire Protection Association Standard 211 says, “Chimneys,
fireplaces, and vents shall be inspected at least once a year for soundness, freedom from deposits, and correct clearances. Cleaning,
maintenance, and repairs shall be done if necessary.” This is the national safety standard and is the correct way to approach the
problem. It takes into account the fact that even if you don’t use your chimney much, animals may build nests in the flue or there may be
other types of deterioration that could make the chimney unsafe to use.
The Chimney Safety Institute of America recommends that open masonry fireplaces should be cleaned at 1/4″ of sooty buildup, and
sooner if there is any glaze present in the system. Factory-built fireplaces should be cleaned when any appreciable buildup occurs. This
is considered to be enough fuel buildup to cause a chimney fire capable of damaging the chimney or spreading to the home.
Many American homeowners think their chimneys only need to be cleaned and inspected if they burn wood in their fireplaces or wood
stoves. But almost all heating appliances, whether they burn gas, oil, wood or coal, rely on the chimney to safely carry toxic gases
produced by the heating system of the house.
Each fall, homeowners shift into home-improvement mode. They clean gutters, garages and basements — preparing homes for winter.
But they usually don’t inspect, repair or clean their chimneys, despite the potential for damage to their property or even to their lives.
5,500 fires were attributed to chimneys and chimney connectors serving heating
systems burning liquid and other fuels. As a result of these fires, 130 people died, 230 people were injured, and total property losses
were set at more than $184.4 million.
In addition there were a minimum of 119 deaths from carbon monoxide and at least 4,700 “injuries” reported for the same time frame,
though most estimates range much higher.
The root cause of most of these losses is that most U.S. homeowners are unaware that chimneys are an integral part of a home heating
system and that they require regular evaluation and maintenance. In a great many European countries – including Sweden, Norway,
Denmark, Finland and Germany – chimney-fire damage statistics have been reduced to negligible numbers because national coalitions of
government, insurance companies, fire and building officials, and chimney sweeps have developed tough regulations mandating regularly
scheduled chimney inspections and cleaning. The citizens of those countries understand the hazards of unmaintained chimneys, and
their chimney sweeps are regular members of their home safety team.
Most homeowners in the U.S. and Canada, however, seem to have little working knowledge of chimney and venting systems. This
situation is complicated by the fact that faults, damage and problems rarely visible to the casual observer. In fact, people who will quickly
replace a faulty automobile exhaust system because of the hazard it presents will allow their home’s exhaust system the chimney or vent –
to go unchecked and unmaintained for years. The threat of chimney fires and unsafe indoor air quality conditions can be greatly reduced,
perhaps even eliminated, if homeowners only understood that chimneys are active home operation systems which require regular
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, 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. Carbon monoxide detectors are now readily available and
no home should be without at least two, one near the furnace and one near the sleeping area of the home. Detectors are NOT a
substitute for routine maintenance, but can be a lifesaver should problems occur.
Considering the risks involved when gas or oil systems are neglected, and the benefits that accrue when they are properly maintained,
we suggest you have your furnace serviced yearly by a qualified technician and your chimneys checked annually by a C.S.I.A. Certified
Chimney Sweep and cleaned or repaired .