Atlanta Home Inspection-certified member ICC,

These areas are the most dangerous if faulty installations,damage flues,improper connections.Have your heating systems if gas or propane energy is used and fire places checked annually.A home inspector will charge far less on componets than Hvac tech who will try to sell you repairs.

Combustion gases and particles also come from chimneys and flues that are improperly installed or maintained and cracked furnace heat exchangers.  Pollutants from fireplaces and woodstoves with no dedicated outdoor air supply can be "back-drafted" from the chimney into the living space, particularly in weatherized homes.

Carbon monoxide is a colorless, odorless gas that interferes with the delivery of oxygen throughout the body.  At high concentrations can cause a range of symptoms from headaches, dizziness, weakness, nausea, confusion, and disorientation, to fatigue in healthy people and episodes of increased chest pain in people with chronic heart disease.  The symptoms of carbon monoxide poisoning are sometimes confused with the flu or food poisoning.  Fetuses, infants, elderly people, and people with anemia or with a history of heart or respiratory disease can be especially sensitive to carbon monoxide exposures.Water heater that use gas may have leaky lines,inadequate air supply for proper combustion.Gas fire furnaces as well.

Nitrogen dioxide is a colorless, odorless gas that irritates the mucous membranes in the eye, nose, and throat and causes shortness of breath after exposure to high concentrations.  There is evidence that high concentrations or continued exposure to low levels of nitrogen dioxide increases the risk of respiratory infection; there is also evidence from animals studies that repeated exposures to elevated nitrogen dioxide levels may lead, or contribute, to the development of lung disease such as emphysema.  People at particular risk from exposure to nitrogen dioxide include children and individuals with asthma and other respiratory diseases.

Particles, released when fuels are incompletely burned, can lodge in the lungs and irritate or damage lung tissue.  A number of pollutants, including radon and benzo(a)pyrene, both of which can cause cancer, attach to small particles that are inhaled and then carried deep into the lung.

Consider potential effects of indoor air pollution if you use an unvented kerosene or gas space heater.  Follow the manufacturer's directions, especially instructions on the proper fuel and keeping the heater properly adjusted.  A persistent yellow-tipped flame is generally an indication of maladjustment and increased pollutant emissions.  While a space heater is in use, open a door from the room where the heater is located to the rest of the house and open a window slightly.
 
Install and use exhaust fans over gas cooking stoves and ranges and keep the burners properly adjusted.

Using a stove hood with a fan vented to the outdoors greatly reduces exposure to pollutants during cooking.  Improper adjustment, often indicated by a persistent yellow-tipped flame, causes increased pollutant emissions.  Ask your gas company to adjust the burner so that the flame tip is blue.  If you purchase a new gas stove or range, consider buying one with pilotless ignition because it does not have a pilot light that burns continuously.  Never use a gas stove to heat your home.  Always make certain the flue in your gas fireplace is open when the fireplace is in use.
 
Keep woodstove emissions to a minimum.  Choose properly sized new stoves that are certified as meeting EPA emission standards.

Make certain that doors in old woodstoves are tight-fitting.  Use aged or cured (dried) wood only and follow the manufacturer's directions for starting, stoking, and putting out the fire in woodstoves.  Chemicals are used to pressure-treat wood; such wood should never be burned indoors.Have central air handling systems, including furnaces, flues, and chimneys, inspected by a certified building inspector annually and properly look for cracks or damaged parts.

Blocked, leaking, or damaged chimneys or flues release harmful combustion gases and particles and even fatal concentrations of carbon monoxide. 

Strictly follow all service and maintenance procedures recommended by the manufacturer, including those that tell you how frequently to change the filter.  If manufacturer's instructions are not readily available. change filters once every month or two during periods of use.  Proper maintenance is important even for new furnaces because they can also corrode and leak combustion gases, including carbon monoxide.

   The living rooms of many homes in the United States have attractive masonry fireplaces. Some people use them for added warmth (a secondary source of heat) on very cold days. Others burn wood in their fireplaces to create a cozy ambiance in the evening or on the weekend.

Conventional masonry and factory-built fireplaces are not efficient at producing heat. These fireplaces are also the source of smoke, indoors and out. To reduce the health risks of smoke—for you, your family, and your neighbors, I recommend installing a fireplace insert, a vented gas stove, or a pellet stove.

Fireplace inserts give you the same efficient performance as wood stoves. A certified insert is similar to a freestanding wood stove, but it has been modified by the manufacturer to fit a fireplace opening (see cross-sectional illustration at right). The insert converts a fireplace into a much more efficient, lower polluting heating system.

A certified inspector will make sure to check proper installations of the flue liner in your masonry chimney. Lining the chimney helps maintain a proper draft and prevents icing, which can block the flow of air through the system.