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Note: This Instructional Module information comes from our Training Manual. The complete Training Manual can be ordered from our Program and comes with a video, transparency masters, module publications, and many other educational resources.Module Learning Objectives
Support Publications
Video (See "IAQ Video Sampler" included with the manual)
Notes to the Program Leader:On the following pages are reproductions of 42 overhead transparencies and suggested discussion points for each transparency on the general topic of indoor air quality (IAQ). This section covers issues related to indoor air management, energy conservation and IAQ, excess moisture and biological pollutants, radon, combustion products, formaldehyde, and volatile organic compounds. For a one-hour presentation, all 42 overhead transparencies are appropriate. For a 30-minute presentation, the following transparencies are suggested: 1, 2, 4, 5, 6, 7, 8, 10, 12, 13, 14, 16, 17, 27, 28, 29, 30, 32, 33, 34, 35, 37, 42.This section provides an overview of potential residential indoor air pollutants. The overview is useful for introducing the topic to homeowners, renters, builders, real estate brokers, local government officials, and others interested in housing issues. After attending this presentation, participants will understand there is no single test to perform in a home to identify all pollutants present. They will realize the importance of controlling pollutants at their sources and taking preventive steps to maintain healthy levels of indoor air quality in their homes. As you prepare for the presentation, use this manual for background information. There are a number of easy-to-read publications that provide more detailed information on each pollutant discussed in this section. You may use this presentation as an introductory session that can be followed up with in-depth presentations on one or more of the pollutants discussed. For example, the "Combustion Pollutants in the Home" module would be a timely presentation to give just before the heating season begins, and it could be augmented with news releases on the dangers of carbon monoxide. If you wish to speak with experts as you prepare for your presentation,
a good starting point is the U.S. Environmental Protection Agency's lndoor
Air Quality lnformation Clearinghouse. Information Specialists are available
at 1-800-438-4318. There are also many sources of information on the World
Wide Web which you can find through a Net Search using the key words "indoor
air quality." Finally, depending on resources available at your state's
land grant university, you may be able to talk to a State Extension Specialist
with expertise in this area.
Script for Transparency #1 In recent years, a growing body of scientific evidence has indicated the air people breathe inside their homes can be more seriously polluted with dangerous toxins than outdoor air in even the largest and most industrialized cities. The growing awareness of this issue is causing indoor air pollution to become a national health concern. The issue is important because most people spend about 90% of their
time indoors. Other people, such as the elderly and infirm, may spend all
of their time indoors. The matter is serious when you consider that toxin
levels in indoor air can be higher than what is permitted by federal regulations
in outdoor air. This was the case in nearly all homes examined in a study
of this subject.
Script for Transparency #2 Indoor Air Management The growing awareness of indoor air pollution is giving rise to indoor air management as a new consumer skill. Three separate aspects of indoor air management are pollutant identification, source control, and mitigation. Let's consider each of these points. Pollutant identification. Unfortunately, there is no single test that can be used to identify all possible pollutants in the air of your home. Separate tests are conducted for each pollutant. If you think something in the air of your home is making you sick, you should see your doctor, who can tell you if your symptoms are related to a pollutant. Then you can go about testing for that pollutant. But this does not work for pollutants for which there are no immediate adverse health symptoms. For these, it is best to follow guidelines that have been established by the U.S. Environmental Protection Agency. Source control. Source control refers to the prevention of indoor air pollution by not allowing the sources of pollutants in your home in the first place. This is the most effective air quality control measure. Mitigation. Even in homes where great care has been exercised
to prevent indoor air pollution, a pollutant may be found. In that case,
it can be removed by what are called mitigation measures.
Many people incorrectly assume that energy conserving or "energy tight" homes are more susceptible to indoor air pollution than homes kept deliberately leaky. These people may be surprised to learn that properly designed and maintained energy efficient homes can have a better quality of indoor air than leaky, drafty homes. This is because in new, energy efficient homes, and in older homes that
have had energy conservation features correctly installed, many pollutants
are less likely to enter the homes, and those that do can be removed with
controlled ventilation. Remember, in a home that is left intentionally
leaky, there is no way to control the air that enters through cracks and
other openings. That air flow is affected by wind speed, topography, and
vegetation. On the other hand, energy efficient homes use exhaust fans
to remove excessive moisture and cooking odors, and a tight building shell
ensures toxins in soil gas do not enter the home.
Script for Transparency #4 What are the pollutants that can be found in the air of a home? This
transparency shows that these pollutants include biological contaminants,
radon, combustion products, organic gases, lead, and asbestos. In the following
transparencies, we will discuss what these pollutants are, where they come
from, and what can be done to control them.
Script for Transparency #5 Biological Contaminants Many of us have heard the phrase, "tight houses sweat," which refers
to the fact that indoor moisture, if not controlled properly, can build
up to levels which can cause condensation problems. We may see this condensation
directly (such as when it builds up on windows) or indirectly (such as
mold and mildew). Uncontrolled moisture levels in homes can lead to structural
problems from rotting studs and joists. In addition to damaging our homes,
uncontrolled moisture levels can adversely affect human health.
Script for Transparency #6 This chart summarizes research that has been conducted on what happens at different levels of relative humidity (RH). Note that humidity levels from 0% to 100% are shown on the horizontal line. If we go down the list on the vertical line, we can see that bacteria populations are high at low levels of RH, drop off at 30% RH, then begin to increase again at 60% RH. Levels of viruses are high at low RH levels till about 50% RH, then begin to increase again at 70% RH. Fungi and dust mites need moisture to survive. We begin to see fungal growth at 60% RH and mites at 50% RH. Research on respiratory infections and RH is limited, but suggests that more infections occur at lower levels of RH. Allergy problems and asthma occur at both low and high RH levels. Chemical interactions (here the main interaction is formaldehyde emission) begin at about 30% RH and increase as RH increases. Ozone is a respiratory irritant that is produced by some appliances. Its levels are highest at low levels of RH. The main feature of this chart is that there is an optimum zone of RH
between 40% and 60%, where the presence of all these pollutants is minimized.
However, be aware that in very cold weather, moisture levels in the home
over about 50% RH can cause condensation problems, leading to the growth
of mold and mildew.
Script for Transparency #7 Warm air is capable of holding more moisture than cold air. In this
transparency, the cube on the left represents air at 75o Fahrenheit
and a relative humidity of 30 percent. That means that the air is holding
30 percent of the moisture it is capable of holding. When this same cube
of air, with the same amount of moisture, is cooled to 40o Fahrenheit,
it is capable of holding less moisture, and is now at 100 percent relative
humidity.
Script for Transparency #8 When air is at 100 percent relative humidity, it is said to be saturated.
This is called the dew point temperature -- the temperature at which water
vapor condenses to liquid. We see this occurring in many ways. For example,
on a hot, muggy afternoon in the summer, moisture forms on the outside
of a glass of iced tea. This happens because the air near the glass cools,
and moisture from the air condenses on the glass. In a home during winter,
moisture-laden air cools as it approaches a window and, therefore, condenses
on the window.
Script for Transparency #9 What are some sources of moisture in a home? Moisture is produced by
common household activities such as cooking, cleaning, and taking showers.
People, plants, and pets also produce moisture.
Script for Transparency #10 The average household of four adds between three and six gallons of
water in a day to the air. A person gives off three pints of moisture a
day by breathing. Cooking and dishwashing produce about one pint of water
per meal. And about one-half pint of moisture is released into the air
from taking a shower.
Script for Transparency #11 Crawlspaces and basements are also sources of moisture in a home, especially
if they have dirt floors not covered by a moisture barrier. Moisture migration
can occur through the soil into a home. And any water that leaks into crawlspaces
or basements can raise moisture levels throughout the house.
Script for Transparency #12 The key to controlling relative humidity levels in a home is to maintain a moisture balance. Remember, some moisture in the air is necessary for human health and comfort, but too much moisture can cause problems. A moisture balance is maintained by making sure a home has positive
exterior drainage away from the house in all directions, a properly sized
heating and cooling system, vapor diffusion protection (through the installation
of vapor retarders where needed), as well as adequately planned ventilation,
especially at points where moisture is produced.
Script for Transparency #13 Inside the home, moisture should be vented to the outside from the point at which it is produced. This means that a kitchen stove needs an exhaust fan over it, which should be ducted to the outside. A circulating fan may remove some cooking odors from the air, but it will not remove moisture. A bathroom also needs an exhaust fan that leads to the outside. This
fan should be used when anyone is taking a shower and for a short time
afterwards, until moisture levels have decreased to the point that there
is no condensation on windows and mirrors. In the laundry room, a clothes
dryer should be vented to the outdoors.
Script for Transparency #14 This chart shows when surface condensation occurs on windows. You can see that depending on the type of windows you have in your home, condensation will occur at different levels of relative humidity. For example, when the temperature inside is 70o Fahrenheit
and it is 0o Fahrenheit outside, condensation will occur on
the interior surface of a single-pane window when the indoor relative humidity
level is 15 percent; on a double-pane window at 42 percent; and on a low-emissivity
window at 65 percent. You can see that by increasing the energy efficiency
of your windows, you can lessen the incidence of condensation. This happens
because the inside glass surface does not get as cold.
Script for Transparency #15 Radon Since the mid-1980s, radon gas in the home environment has been recognized
as a significant health hazard. While the presence of elevated levels of
the gas in a home is a serious issue, there are proven methods that are
in many cases simple to implement that can successfully reduce dangerous
concentrations of the gas. This next group of transparencies describes
what radon is, where it comes from, what can be done to test for its presence,
and if necessary lower its levels in a home.
Script for Transparency #16 Radon is a colorless, odorless, radioactive gas that results naturally
from the decay of uranium and radium. Radon is found in low amounts in
soils all over the world.
Script for Transparency #17 Once radon comes in contact with a house, it can be drawn inside through
cracks or other openings in foundation walls and concrete floors. Some
of these other openings include sump holes, French drains, and utility
pipes or wires that penetrate a foundation wall. Radon has been found to
contaminate some private water supplies as well. Once in water, radon is
released into the air of a house when the water is aerated at dishwashers,
clothes washers, faucets, and showers. There have also been isolated instances
of radon emanating from contaminated construction materials.
Script for Transparency #18 After it enters a house, radon continues to decay, and microscopic solid
particles are formed. These particles are also radioactive. They can easily
become attached to other solid objects (such as dust or smoke) which can
then be inhaled into people’s lungs. Radiation released from these particles
can then damage lung tissue and can eventually cause lung cancer.
Script for Transparency #19 How can we test for radon? One way of detecting its presence is to use a canister of activated charcoal, which costs about $15. Once opened and set in place for a specified period (anywhere from two to seven days), radon in the air is adsorbed, or collected onto the surface of the charcoal granules. The first measurement taken in a house is known as the screening measurement, and it helps to determine whether more measurements should be made. When the test period is completed, the canister is sealed and sent back
to the testing company. After it has been analyzed, you will receive a
report on the radon level. Because radon concentrations vary with time,
the screening measurement from a charcoal canister should only be used
as an indicator of a potential problem. A year-long measurement can give
a better idea of average radon levels in a house.
Script for Transparency #20 Another radon testing method uses an alpha track detector, which costs
about $25. Instead of measuring radon gas, this device records radiation
damage from radon decay products on a plastic film inside the canister.
This type of detector is kept in place for a period of three months to
a year. As with the charcoal canister, it is sent to a laboratory for analysis.
Script for Transparency #21 To better understand how radon enters a house, and how the gas and its
decay products move about once inside, lets consider these next few transparencies
which illustrate air movement principles.
Script for Transparency #22 A house comes under positive pressure when air is blown into it; for
example, by using a window fan directed inside. The house comes under negative
pressure when air is drawn out of it. This can happen when exhaust fans
or combustion appliances are used. A house is under neutral pressure when
it is at equilibrium with outdoor pressure. This can happen when windows
on all sides of a house are open.
Script for Transparency #23 Combustion appliances, such as furnaces, boilers, woodstoves, fireplaces, space heaters, gas dryers, and water heaters, need oxygen to support their flames. When combustion air is drawn from inside the house, the house comes under negative pressure, which causes air to be pulled inside through cracks and other openings in the building shell, as well as from soil beneath the house. Exhaust fans that are not provided with make-up air can also cause negative pressure. To prevent a house from coming under negative pressure, combustion appliances
should be provided with a source of air from outside the house. New appliances
are designed this way. Exhaust fans should also have a source of air from
outside the house. This can be accomplished by using a fan with an outdoor
air supply duct, or by installing specially designed vent openings in exterior
walls.
Script for Transparency #24 Heat radiates in all directions, but warm air rises. In a house that
is not energy efficient, some of the warm air escapes through cracks and
other openings in the upper levels of the structure, and is then replaced
by cooler air which enters the house at lower levels, as well as from soil
beneath the house. Chimneys for combustion appliances can also create a
stack effect (as air is pulled up and out of a chimney) even when the appliance
is not operating.
Script for Transparency #25 This transparency shows a section view of a basement. The basement wall has been finished by installing studs against the wall and insulating between them with fiberglass. Notice that radon can enter this basement through openings in the finished wall, such as the electric receptacle. There is also a crack in the concrete floor that serves as another radon entry route. Once inside the basement, radon can be drawn into unsealed furnace ducts
and distributed throughout the house by the ductwork and registers. Radon
can also be drawn into the living space through openings around pipes in
floors.
Script for Transparency #26 A first step in preventing the entry of radon gas into a home involves
sealing all openings to the soil, such as this settling crack in a foundation
wall. Settling cracks occur in foundation walls and in concrete floors.
These cracks can be filled with cement grout if they are large enough;
small cracks can be filled with high quality caulking compounds suitable
for concrete. However, sole reliance on sealing cracks in basement walls
and floors is usually not an effective radon remedy, especially in a finished
basement where many cracks will probably be overlooked.
Script for Transparency #27 A very effective radon mitigation method diverts radon from a house at its source, through soil gas suction. In this system, a plastic pipe is installed through a concrete floor to the gravel beneath the slab. The pipe extends to the attic of the house and through the roof. Here, a special fan (called an in-line fan) draws radon gas out of the soil from beneath the house and pulls it upward through the pipe. The pipe then exhausts the radon gas to the outside, where it is diluted
with outdoor air. This method of radon removal is effective because it
addresses the pollutant at its source: the soil beneath the basement floor.
Radon is removed from the soil and sent outside, before it has a chance
to enter the house.
Script for Transparency #28 At this time, there is no reliable method for testing a building site to determine if radon is going to be a problem in a house to be built there. The best way to avoid a potential radon problem is to take preventive steps during construction. Many of these steps are similar to those implemented for waterproofing
a house, such as treating a foundation wall and installing traps in floor
drains. Other steps, such as soil suction, are new but cost very little
when a house is first being built. Some builders will install part of a
soil gas suction system, such as the pipe without the fan. If radon is
determined to be present in the new house, the fan will be installed later.
Script for Transparency #29 Combustion Products Woodstoves, kerosene heaters, fireplaces, furnaces, boilers, water heaters, and other fuel-burning appliances (as well as tobacco smoke) are all potential sources of combustion products in a home. Some of these harmful products include: carbon monoxide, which can be lethal at high concentrations; nitrogen dioxide, which can cause respiratory irritation and chronic bronchitis; and respirable particles, the solid particles in smoke from tobacco, wood, gas, and oil. If released into household air, these particles become suspended in the air and can then be inhaled and cause respiratory problems. Furnaces, water heaters, woodstoves, and ranges typically do not cause
indoor air problems if they are properly installed, vented to the outside,
and maintained. When a furnace is not maintained, however, a problem such
as a cracked heat exchanger or blocked flue can allow combustion products
into a home. Pollutants produced during food preparation can spread throughout
a house if a range exhaust fan is not used.
Script for Transparency #30 Exposure to combustion products in a home can be reduced by not using
any unvented fuel-fired space heaters indoors; by properly maintaining
your heating system; by not smoking in the home; and by using exhaust fans
over gas stoves. The importance of exterior-vented exhaust fans over kitchen
stoves has already been mentioned for moisture control. With a gas stove,
an exterior-vented fan is also important for removing combustion products
of the gas flames.
Script for Transparency #31 This transparency shows a heating system technician performing an annual check on a furnace. This annual maintenance is important for preventing the entry of combustion products into the home. Necessary adjustments to the fuel burner will be made during this time
to make sure the air-fuel mixture is correct. Soot will be cleaned away
from the heat exchanger surface, and the heat exchanger will be inspected
for any possible cracks. The exhaust vent should also be checked to assure
it is intact and unblocked.
Script for Transparency #32 Because carbon monoxide (CO) is a colorless, odorless gas, you cannot detect its presence until it causes problems. CO alarms are now available in several forms. You can purchase small, button-shaped alarms that change color if CO levels are high, and you can also purchase alarms that produce an audible sound at harmful CO levels. If you suspect that your home has a problem with carbon monoxide, call
your utility company and ask that a technician come to your home to perform
a test. Regular maintenance of combustion appliances, such as furnaces
and boilers, is the best way to prevent these appliances from releasing
carbon monoxide into the home.
Script for Transparency #33 Organic Gases In the field of chemistry, the term "organic" refers to carbon-based compounds. Life on earth is based on organic molecules -- those that contain carbon, hydrogen, and oxygen. How those atoms are arranged affects many things, including: interactions with other molecules, freezing and boiling temperatures, smell, and living things, including people. Volatility means that a compound tends to exist as a vapor or gas at
normal indoor conditions. There are hundreds of volatile organic compounds
(VOCs) in indoor and outdoor air, many of which have adverse impacts on
human health. Many VOCs are present in household products, and many are
known or suspected carcinogens. Benzene, for example, is a carcinogen,
and Xylene may injure the heart, liver, kidney, or nervous system at high
concentrations.
Script for Transparency #34 Common sources of VOCs include paints, paint strippers and other solvents, aerosol sprays, cleansers and disinfectants, moth repellents, air fresheners, stored fuels, automotive products, hobby supplies, and dry-cleaned clothing. Some ways to reduce exposure to VOCs include:
It is particularly important to take as many of these steps as possible
while you are involved in short-term activities that can generate high
levels of pollutants. For example, some of these activities include painting,
paint stripping, heating with kerosene heaters, and engaging in hobby activities
such as welding, sanding, or soldering. If possible, you might also choose
to do some of these activities outside if the weather permits.
Script for Transparency #35 Formaldehyde is a VOC with a strong odor. It is emitted from various construction materials, including plywood wall paneling, particle board, fiberboard, and furniture and cabinetry made from these products. Formaldehyde is also used as a component of some glues and adhesives, and as a preservative in some paints and coating products. Formaldehyde is sometimes used to add permanent-press qualities to clothing and draperies. Because this pollutant is also a product of combustion, other sources include unvented, fuel-burning appliances and secondhand smoke (environmental tobacco smoke). Exposure to formaldehyde can cause watery eyes; nose, throat, and eye
irritation; and breathing difficulties. High concentrations may trigger
asthma attacks in certain people as well. Additionally, formaldehyde has
been shown to induce cancer in animals and may have this same effect on
people.
Script for Transparency #36 To reduce exposure to formaldehyde, use exterior grade plywood instead
of interior grade plywood, because it is formulated differently and emits
the gas at lower rates. Some research has indicated that coating pressed
wood products with polyurethane (including all surfaces and edges) may
reduce formaldehyde emissions. As we saw earlier in this presentation,
controlling humidity levels will minimize formaldehyde emissions. Of course,
the best strategy to reduce exposure to formaldehyde is to avoid the use
of products that contain it.
Script for Transparency #37 Lead and Asbestos Existing homes can be contaminated with lead (which used to be an ingredient in paint and pipe solder) and asbestos (which was used as insulation for boilers, pipes, and ducts, and in the formulation of floor tiles, roof tiles, and exterior shingles). Exposure to lead can occur through ingesting paint chips, inhaling lead
dust, or drinking contaminated water. In addition, the soil around homes
near roads may be contaminated with lead from years of exposure to gasoline
exhaust fumes.
Script for Transparency #38 Lead exposure can damage the central nervous system. In children, this
can result in lowered IQ scores, and birth defects can occur if pregnant
women are exposed. A blood test is administered to determine a person's
blood-lead level.
Script for Transparency #39 Lead abatement is not a "Do-It-Yourself" activity. Careless removal
can pose serious health risks. Home testing kits can identify sources of
lead in a home, but these may not detect low levels. Specialized, licensed
lead abatement contractors are trained in the safe removal or encapsulation
of this pollutant.
Script for Transparency #40 Asbestos Exposure to asbestos can cause lung cancer, asbestosis, and mesothelioma.
Asbestos-containing materials should not be disturbed in a home, except
by an asbestos abatement contractor.
Script for Transparency #41 Asbestos-containing materials pose a hazard when they are friable --
that is, when they are flaking or crumbling. If this is the case, an asbestos
abatement contractor will remove the material, or will encapsulate it by
coating the material with a sealant or enclosing it in an airtight structure.
Script for Transparency #42 Earlier in this presentation, three aspects of indoor air management
were listed: pollutant identification, source control, and mitigation.
These strategies apply to individual pollutants and, when utilized as an
overall plan, will assure that the air in our homes is healthy to breathe.
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