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Hazardous products of oil or gas heating appliance fuel combustion: this article explains flue gases and particles produced by various heating appliances and their impact on safety and indoor air quality in homes.
A combustion appliance is any device that burns fuel
for heating, cooking, or decorative purposes. This includes
central-heating systems, space heaters, water heaters,
ovens and cooktops, woodstoves, and fireplaces. The
major pollutants associated with combustion are carbon
monoxide, nitrogen dioxide, sulfur dioxide, and particles. See INDOOR COMBUSTION PRODUCTS & IAQ for a Table of Combustion Products & Indoor Air Quality Hazards that accompanies this article.
Unvented space heaters and gas stoves without range
hoods dump combustion products directly into the living
space and have no place in the modern home. Vented appliances,
such as boilers, water heaters, and fireplaces, are
designed to exhaust combustion products to the outdoors,
but they are vulnerable to backdrafting in today’s tightly
built houses. When appliances are malfunctioning or out
of adjustment, they produce more pollutants, including
carbon monoxide. The combination of backdrafting and
the high production of carbon monoxide can be deadly.
Health Effects of Combustion Products. Possible
health effects from combustion products include eye and
respiratory irritation, persistent coughing, headaches,
fatigue, and dizziness. In the case of carbon monoxide,
symptoms can include nausea and confusion, and, at very
high levels, loss of consciousness and death. Effects associated
with specific pollutants are discussed below:
Carbon monoxide. CO is a colorless, odorless gas
produced by incomplete combustion. Common
sources include blocked chimneys or vents, cracked
or rusted heat exchangers, poorly adjusted appliances,
smoldering fireplaces, and auto exhaust from an
CO interferes with the blood’s ability
to deliver oxygen to the body. Low concentrations
may increase chest pain in people with heart disease.
Sustained concentrations above 70 ppm can cause
fatigue, headache, weakness, and nausea, and may
be confused with the flu or food poisoning.
infants, the elderly, and people with anemia or heart
disease are especially vulnerable. At very high
levels, CO causes confusion, loss of consciousness,
and death. CO alarms are programmed to sound
before levels reach 100 ppm for 90 minutes,
200 ppm over 35 minutes, or 400 ppm over
see CARBON MONOXIDE - CO for details about carbon monoxide standards, exposure, testing, and remediation.
Nitrogen dioxide. NO2 is a colorless gas with an acrid
odor at high levels.
T he primary source of NO2 in
homes is unvented gas and kerosene space heaters,
gas stoves without a range hood, and stoves with
continuously burning pilot lights. Studies have shown
that homes with unvented gas appliances have
elevated NO2 levels, and there is some evidence linking
this with impaired lung function and increased respiratory
infections in children. At high levels, NO2 is
an eye, nose, and respiratory irritant.
people with asthma and other respiratory problem are
more susceptible to exposure.
Common Indoor Pollutants and Sources 293
Sulfur dioxide. SO2 is a colorless gas with a pungent
odor and is primarily associated with oil- and coal-
burning appliances. At low levels of exposure, SO2
can cause eye, nose, and respiratory tract irritation.
At high exposures, it can cause the airways to narrow,
leading to chest tightness and breathing problems.
People with asthma are particularly susceptible to
SO2 exposure. See Sulfur Dioxide Gas.
Particles. The health effects of breathing particles
depend on several factors, including the size and
chemical makeup of the particles.
suspended particles can cause eye, nose, and throat
irritation, and increased respiratory symptoms for
people with chronic lung or heart disease. In addition,
a number of pollutants, including the carcinogens
radon and benzo(a)pyrene, attach themselves to
small particles and are then inhaled and carried deep
into the lungs.
Guide to Reducing Exposure to Combustion Gases & Particles Indoors
The three main sources of combustion
products in household air are unvented appliances,
appliances or flues that are broken or poorly adjusted, and
backdrafting. To minimize exposure, follow these general
Unvented space heaters. Do not use unvented
space heaters in living spaces. If required for
temporary use, closely follow manufacturer’s
directions, open a window, and open doors to
adjoining rooms. A persistent yellow-tipped flame
is generally an indicator of poor adjustment and
Cooking. With gas ranges and cooktops, always use
a range hood vented to the exterior. Choose appliances
with electronic ignition rather than a continuously
burning pilot light. Or replace with electric
Sealed combustion. In new construction, avoid the
use of atmospherically vented boilers, furnaces, or
water heaters. Instead, use power-vented appliances,
preferably with sealed combustion.
Inspections and maintenance. Have central heating
systems and water heaters inspected and adjusted
annually. Inspect all flues and chimneys for blockages
or damage and promptly repair any problems.
Woodstoves. Make sure doors in older woodstoves are
tight fitting with intact gaskets. New stoves should
meet EPA emissions standards. Burn only seasoned
wood. Make sure there is adequate air for combustion
and that the house is not depressurized by exhaust fans
(see Backdrafting and also page 295 of Best Practices Guide to Residential Construction).
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Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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