Fighting Mold — The Homeowners' Guide
Understanding mold
 | Mold can be harmful or helpful—depending on where
it grows.
| Mold needs moisture to grow.
| Mold does not grow on dry materials.
| Mold growing inside a home can affect the occupants.
| Occupants can learn to recognize mold. |
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What are molds?
Molds are microscopic fungi, a group of organisms which
also includes mushrooms and yeasts. Fungi are highly adapted to grow and
reproduce rapidly, producing spores and mycelia in the process.
You encounter mold every day. Foods spoil because of
mold. Leaves decay and pieces of wood lying on the ground rot due to mold.
That fuzzy black growth on wet window sills is mold. Paper or fabrics
stored in a damp place get a musty smell that is due to the action of
molds.
Molds can be useful to people. The drug Penicillin is
obtained from a specific type of mold. Some foods and beverages are made
by the actions of molds. The good kinds of molds are selected and grown in
a controlled fashion.
Molds are undesirable when they grow where we don’t
want them, such as in homes. Over 270 species of mold have been identified
as living in Canadian homes. Molds that grow inside may be different from
the ones found outdoors.
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 What makes molds grow?
Molds will grow if we provide them with moisture and
nutrients. If we keep things dry, molds do not grow. High moisture levels
can be the result of water coming in from the outside, through the floor,
walls or roof; or from plumbing leaks; or moisture produced by the people
living in the home, through daily activities like bathing, washing clothes
or cooking. Water enters the building when there is a weakness or failure
in the structure. Moisture accumulates within the home when there is not
enough ventilation to expel that moisture.
Different kinds of molds grow on different materials.
Certain kinds of molds like an extremely wet environment. Other kinds of
molds may be growing even if no water can be seen. Dampness inside the
material can be enough to allow them to grow.
Why are molds a concern?
Damage to materials is one concern. Materials get
stained or discolored, and over time they are ruined. Moldy paper and
cardboard disintegrate over time. Fabrics are damaged. Continued mold
growth can be indicative of moisture conditions favorable for growth of
fungi that cause wood rot and structural damage.
When molds are growing inside the home, there may be
health concerns. Molds release chemicals and spores.
Health experts indicate that, depending on the type of
mold present in a home, the amount and degree of exposure, and the health
condition of the occupant, the health effects of mold can range from being
insignificant to causing allergic reactions and illness.
Pregnant women, infants, the elderly and those with
health problems, such as respiratory disease or a weakened immune system,
are more at risk when exposed to mold. Consult your family physician if
you believe there is someone who may be at risk.
How can you tell if it is mold?
Discoloration
Discoloration is a sign of mold. However, all
discoloration is not due to mold. Carpeting near baseboards, for example,
can be stained by outdoor pollution entering the home. Stains or soot may
also be caused by the smoke from burning candles or cigarettes.
Mold may be any colour: black, white, red, orange,
yellow, blue or violet. Dab a drop of household bleach onto a suspected
spot. If the stain loses its colour or disappears, it may be mold. If
there is no change, it probably isn’t mold.
Smell/Odour
Sometimes molds are hidden and cannot be seen. A musty
or earthy smell often indicates the presence of molds. But a smell may not
be present for all molds. Even when you don’t notice a smell, wet spots,
dampness or evidence of a water leak are indications of moisture problems
and mold may follow.
Is there a mold problem?
Molds are always found in the air outside and in all
buildings. They come into the home in many ways —through open windows or
doors, on clothing, pets, food or furniture. The problem starts when mold
grows inside the home.
Some mold growing, for example on the window sill but
not elsewhere, is not a cause of concern. You can clean the mold yourself.
The presence of mold is a sign that there is too much moisture in your
home—a situation which must be corrected.
Inspect the home to find the extent of the mold.
How much mold is growing?
One way is to estimate the area of the mold.
Mold is considered to cover a “small area” if
the patch is no larger than a square meter. There should be no more than
three patches, each patch smaller than a square meter. Clean up small
areas yourself using a detergent solution, household rubber gloves and a
dust mask for protection.
Small moldy areas in homes may become larger over time,
if ignored, so it’s important to clean up and remove even small patches
of mold.
The mold area is considered “moderate” if
there are more than three patches, each patch smaller than a square meter,
or there is one or more isolated patches larger than a square meter but
smaller than 3 square metres (size of a 4 x 8 foot sheet of plywood).
Assessment by a professional is recommended. You can
clean up moderate amounts of mold but you must follow the proper
procedures and use the proper protective equipment.
A mold area is considered “extensive” if a
single patch of mold is larger in area than a sheet of plywood. Being
exposed to this much mold is not a good idea. Do not attempt to clean up
large areas of mold yourself. You need professional help to determine why
the mold is there in the first place and how to clean it up.
| Estimate how much mold is growing.
| You can clean up a “small area” of mold yourself.
| For larger mold areas or recurrent mold problems,
seek professional help. |
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When should you seek professional help?
You may need professional help when:
| there is a lot of mold;
| the home is very damp and moist;
| mold comes back after repeated cleaning; and
| a family member suffers from asthma or respiratory
problems or other health problems that appear to be aggravated inside
the home. |
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How do you get professional help?
Contact your local CMHC office for a list of individuals
who have completed the CMHC Residential Indoor Air Quality Investigator
program. A trained IAQ investigator, who operates a private business and
sells his/her services, examines the indoor air quality of your home and
documents your concerns. He/she identifies the problems, finds their
sources and suggests solutions in a written report. Recommendations are
provided to you in an action plan that consists of various options to
improve the indoor air quality in your home.
| “Small areas” of mold can be cleaned with
a detergent solution.
| Wear a mask, safety goggles and rubber gloves.
| Seek professional help if there is a lot of mold or
if mold comes back after cleaning.
| Clean “moderate areas” of mold, but wear proper
protective equipment and follow precautions.
| Seek professional help if there is a lot of mold or
if mold comes back after cleaning. |
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“Small area” clean-up
You can clean up “small areas” of mold (fewer
than three patches, each smaller than a square meter) yourself. The
minimum protective wear needed are:
| safety glasses or goggles;
| a disposable dust mask (3M 8210 or equivalent);
and
| household rubber gloves. |
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Infants and other family members with asthma, allergies
or other health problems should not be in the work area or adjacent room
during the cleaning.
Steps to follow in cleaning up small mold areas
Washable surfaces:
| scrub with an unscented detergent solution; then
| sponge with a clean, wet rag and dry quickly. |
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Using an unscented detergent will make it easier for you
to detect residual moldy odours.
Moldy drywall:
| clean the surface with a damp rag using baking soda
or a bit of detergent. Do not allow the drywall to get too wet. |
Mold that comes back after cleaning is usually an
indication that a source of moisture has not been removed. Seek
professional help from a trained IAQ investigator.
| Clean “moderate areas”of mold, but wear
proper protective equipment and follow precautions.
| Seek professional help if there is a lot of mold or
if mold comes back after cleaning. |
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If you follow the proper procedures and use the proper
protective equipment, you can clean up “moderate areas” of
mold. “Moderate” means more than 3 patches of mold, each
smaller than one square meter, or one or more isolated patches larger than
one square meter but smaller than 3 square metres (size of a 4 x 8 foot
sheet of plywood).
a) Safety precautions
| Wear a disposable dust mask (for example, 3M 8210
or equivalent), glasses or safety goggles and household rubber gloves.
| Isolate the area to be cleaned with plastic sheeting,
taped to walls and ceiling.
| Infants and other family members suffering from
asthma, allergies or other health problems should not be in the work
area or adjacent room during the cleaning. |
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A small clean up should take minutes (not hours) to
finish. When the clean up takes hours to a day to finish, it is suggested
that you upgrade to a better filter, such as a half-face respirator with
charcoal cartridges. An exhaust fan installed in a window in the room
being cleaned would prevent contamination of other areas of the house as
well as provide ventilation.
b) General cleaning
Vacuum surfaces with a vacuum cleaner which has a High
Efficiency Particulate Air (HEPA) filter or is
externally exhausted. Scrub or brush the moldy area with a mild unscented
detergent solution. Rinse by sponging with a clean, wet rag. Repeat. Dry
quickly.
HEPA vacuum the surfaces that were cleaned as well as
surrounding areas.
c) Cleaning wood surfaces
Vacuum mold from wood surfaces using a HEPA or
externally exhausted vacuum. Skip the vacuuming step if the wood is wet.
Clean with a detergent solution then sponge with a clean, wet rag. Extract
the moisture using a dry/wet vac and/or clean, dry rags. Accelerate the
drying with fans and open windows. If the relative humidity outside is
high, use a dehumidifier. The wood should not be allowed to remain wet for
more than a day.
If cleaning with detergent and water does not remove the
mold, try sanding the surface with a vacuum sander (simultaneous vacuuming
and sanding). Do not attempt to sand without vacuuming. This method will
not work if the mold has penetrated to the core of the wood. Severely
moldy wood should be replaced.
d) Cleaning concrete surfaces
Vacuum the concrete surfaces to be cleaned with a HEPA
or externally exhausted vacuum cleaner. Clean up surfaces with detergent
and water. If the surfaces are still visibly moldy, use TSP (trisodium
phosphate). Dissolve one cup of TSP in two gallons of warm water. Stir for
two minutes. Note: TSP must not be allowed to come in contact with skin
or eyes. Saturate the moldy concrete surface with the TSP solution
using a sponge or rag. Keep the surface wetted for at least 15 minutes.
Rinse the concrete surface twice with clean water. Dry thoroughly, as
quickly as possible.
e) Moldy drywall
The paper facings of gypsum wallboard (drywall) grow
mold when they get wet or repeatedly wet and don’t dry quickly. Cleaning
with water containing detergent not only adds moisture to the paper but
also can eventually damage the facing. If the mold is located only on top
of the painted surface, remove it by general cleaning (See Above). If the mold is underneath the paint, the moldy patch and other
moldy material behind it are best cut out and the surrounding areas also
cleaned. This should be done by a mold clean-up contractor. New materials
may become moldy if the moisture entry has not been stopped. If this is
the case, replacement of the materials should be deferred until the source
of the moisture is corrected. The affected areas should be temporarily
covered with plastic sheeting and sealed at the edges.
Any areas that show new patches of mold should be
cleaned promptly.
Dealing with an ongoing problem
| Water entering the home from the outside requires
repair to the building envelope.
| Owners can reduce exposure to mold in their homes. |
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Repair to the building envelope is required if moisture
is entering the home from the outside. At the same time, steps should be
taken inside the home to reduce the occupants’ exposure to mold.
- Discard moldy or damaged materials.Wear a dust mask
and gloves. Furnishings, such as mattresses, carpets, or sofas that
got wet or have been stored in damp conditions should be discarded.
Discard items that are no longer needed. Use this opportunity to
reduce the amount of furnishings—means less materials that absorb
moisture and grow mold. Clothes and other items that have been cleaned
should be stored in sealed plastic bags to prevent re-contamination.
- Proper vacuuming reduces the amount of mold spores.
All surfaces in the home (floors, walls, ceilings, shelves) and
non-washable furnishings (such as sofas, chairs, etc.) must be
vacuumed thoroughly.
- Keep moisture generated within the home to a minimum
by conscientiously following the prevention steps below.
- Pull carpets and furnishings away from walls that get
wet. Carpets and underpads that are moldy should be cut out and
discarded.
- Take steps to dry up areas that get wet. Monitor the
relative humidity of the air. Use a portable dehumidifier, if
necessary. Ensure that the condensate drain pan of the dehumidifier is
emptied regularly.
- If the mold is limited to one area, isolate the area
if possible. Cover the affected surfaces with plastic sheeting secured
at the edges with duct tape. Note that this is only a temporary
measure to minimize your exposure.
- Healthy individuals can regularly clean “small”
and “moderate” areas of mold, thus preventing these from
getting out of hand, by following the safety precautions and cleaning
guidelines.
- Consider seeking professional help from trained IAQ
investigators to identify appropriate remediation steps inside the
home. Removing large amounts of mold will require the services of mold
clean-up contractors.
Preventing mold
| Keep the home dry.
| Find and fix water leaks.
| Discard clutter and excess stored materials.
| Clean and maintain the home regularly.
| Encourage lifestyle practices that reduce moisture. |
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Basic steps to prevent and reduce mold growth
Mold needs moisture to grow. Controlling the moisture
and keeping the home dry prevents the growth of mold.
| Check your home for signs of moisture and molds.
| Find out if water is coming in from the outside and
if substantial moisture is produced inside the home.
| Fix any water leaks promptly.
| Think of the different ways moisture is produced
inside the home (for example, cooking, bathing, plant jungle). Remove
the moisture as it is produced by using exhaust fans. In the absence
of fans, open windows for a short time, but note that the wind can
push the moisture to other parts of the home.
| Measure how much moisture is in the air.To find the
relative humidity in your home, you’ll need a hygrometer. You can
buy one at a hardware store or electronics store.A hygrometer costs
from $5 to $20. Relative humidity in the home should be under 45 per
cent in the winter (or lower to avoid condensation on windows). If
necessary, use a dehumidifier to lower the relative humidity.
| Reduce the amount of stored materials, especially
items that are no longer used. Molds grow on fabrics, paper, wood and
practically anything that collects dust and holds moisture. |
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Mold-proofing your home, room by room
Basement or crawl space
| Reduce the amount of clothes, paper and furnishings
stored in the basement. Discard badly damaged materials. Eliminate
clutter to improve air circulation. Only washable items should be
stored.
| Dehumidify the basement during the warm months.
| Avoid carpets on slab-on-grade or below grade floors.
| Periodically clean the drain in your basement floor.
Use half a cup of bleach, let it stand for a few minutes, then flush
with plenty of water. Keep the drain trap filled with water.
| Avoid standing water. Keep sump pits covered (you can
use plywood wrapped with plastic).
| Regularly clean and replace furnace filters. Use a
pleated one-inch filter, not a coarse filter.
| If you have a heat recovery ventilator (HRV), clean
the filter inside the HRV often.
| If you notice molds or signs of dampness, such as
water on your windows or wet spots elsewhere, do not humidify.
Disconnect furnace humidifiers that are no longer used.
| If you have electric baseboards, vacuum the units, or
have a professional clean them for you. |
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Laundry areas
| Check that your clothes dryer exhausts to the
outside.
| Remove lint every time you use the dryer.
| Don’t hang-dry laundry indoors.
| Dry your laundry tub and washing machine after you
use them. |
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Bathrooms
| Check the bathroom fan to make sure it exhausts to
the outside.
| Turn the bathroom fan on when you shower. Keep it
running for a few minutes after you finish your shower.
| Take short showers.
| Keep surfaces that get wet, such as the walls around
the bathtub and shower, clean and dry.
| If there is a carpet in your bathroom, remove it.
| Check for water leaks.
| Keep drains in good shape by removing debris from
them. |
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To clean a drain:
| Pour a handful of baking soda into it.
| Add a cup of vinegar.
| Put the plug in the drain.
| Let the vinegar and baking soda work for about 20
minutes.
| Run fresh water into the drain. |
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If the drain is still clogged, use a small plumbing
snake.
Kitchen
| If the fan over your stove exhausts outside, use it
when you cook.
| Minimize open boiling.
| Keep your drains in good shape. Follow the steps in
the Bathrooms section, above.
| There’s a drip pan at the back of the refrigerator.
Pull the refrigerator out to clean the drip pan. At the same time,
vacuum dust from the coils at the back of the refrigerator.
| Check under the kitchen sink to make sure there are
no leaks.
| Take out the garbage daily to prevent odours and
spoiling. |
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Closets and bedrooms
| Get rid of clothes and other stored items that you
don’t use. Keeping your closets and bedrooms tidy makes it easier
for air to circulate —and harder for mold to grow. |
Other parts of the home
| A dehumidifier helps to reduce moisture in the home
during the warmer months. Close the windows when the dehumidifier is
running.
| When family and friends come into the home, have them
take off their shoes.
| Vacuum often. If you are buying a vacuum cleaner, try
to get one with a HEPA filter. (See Below)
| Clean hard floors with a damp mop.
| Do not bring in furniture, clothing, books etc. that
have been stored in a moldy place into your home.
| Cut down the number of potted plants in the
house—soil is a good place for mold. |
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Exterior
| Regularly check the condition of the roof and
exterior finish for any places where water might enter.
| Make sure that eavestroughs and downspouts are
connected and working properly and that they are free of debris.
| Install downspout extensions to lead water away from
the building.
| Deal promptly with any problems that you find. |
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Frequently asked questions about mold
Should I have my house air tested for mold?
This is the question most frequently asked by homeowners
who think their home may have a mold problem. Testing is generally not
recommended for homeowners.Testing of moldy materials or an air sample
identifies the types of molds that may be present but does not identify
the cause/source of moisture.The type of mold does not change the
procedures for cleaning up areas of mold less than 3 square meters. You
have to clean up the mold and correct the problem irrespective of the type
of mold. The cost of testing may be better spent hiring a professional
investigator or fixing the problem.
Testing of a moldy material involves sending a swab,
imprint on a Scotch tape or piece of the material to a competent
laboratory. Air sampling requires specialized equipment. An air sample
typically captures mold spores in a period of minutes. Since replicate
samples must be taken due to variations in the airborne molds over time
(even hours) and compared with outdoor samples, air testing is both
expensive and time-consuming. Interpretation of test results may not be
very useful, since there are no advocated "safe levels" of
indoor molds and the results will not tell the health risks from the
molds.
The air feels dry—can I humidify?
Before you add moisture to the air, measure the relative
humidity. Air that feels dry may not be really dry. It may be moldy. High
relative humidity (over 45 per cent) promotes the growth of molds and dust
mites. The moisture in the air may condense on colder exterior walls where
molds start to grow.
If your physician has advised you to use a humidifier in
your child’s bedroom at night, monitor the relative humidity. Turn the
humidifier on and off as necessary. In the morning, take steps to make
sure the room gets dry. Clean and empty the humidifier after each use.
What advantages do HEPA vacuums
provide?
Ordinary vacuums capture large particles only—small
mold spores pass through the vacuum into the air. HEPA vacuums have
special filters that capture small particles. A central vacuum cleaner
which is exhausted to the outside also removes mold spores. A regular
portable vacuum is useful only if its exhaust goes outside the home.
Vacuuming removes settled dust that contains an accumulation of mold
spores over time. Reducing the settled dust reduces molds.
Vacuuming with any vacuum cleaner (ordinary, central or
HEPA) stirs dust and mold during the process. Wear a dust mask so you will
not be breathing more mold.
Is vacuuming with a HEPA or externally exhausted
vacuum cleaner recommended for serious mold problems only?
Vacuum regularly with a HEPA or externally exhausted
vacuum cleaner to prevent the ongoing accumulation of dust and molds. The
need for HEPA or external exhaust vacuuming increases with the severity of
the mold problem.
If a furnishing has been wet at some time in the past or
has been exposed to dampness over a prolonged period of time, vacuuming
with HEPA or externally exhausted vacuum is unlikely to remove the mold
growing beneath the surface. It is better to discard the item.
Where do you find a HEPA vacuum cleaner?
Vacuum cleaner dealers carry HEPA vacuums. Consider
purchasing one as an upgrade to what you may be using. A HEPA vacuum is a
good investment in the long term whether you have mold or not. A generic
canister HEPA vacuum cleaner costs approximately $300. Brand name products
of the same type may cost more.You may inquire if the dealer has a HEPA
vacuum cleaner to rent. Contractors who clean up or renovate houses for
mold should also have this equipment.
Does painting over a moldy surface take care of the
mold?
Painting over mold only masks the problem. Paint does
not kill the mold nor stop it from growing. Surfaces that are washable
should be cleaned with a detergent solution, following the procedure
suggested (See Above),
then allowed to dry. If you are going to paint, remove mold first.
Does cleaning stop the mold growth?
Mold will reappear until its source of moisture is
removed. High moisture levels that are not corrected can make the molds
grow back quickly. Cleaning is only a temporary but essential measure.
You can help by making a conscious effort to keep the
home dry. Obviously, water must be prevented from entering the home. But
you can help by controlling moisture that you produce.
How does one clean clothes that are moldy?
Non-washable clothing can be dry cleaned.
Wash clothes with a detergent solution to which a cup of
bleach is added. Make sure the detergent you use does not contain ammonia.
Repeat as necessary until the moldy odour is gone.
Clothes and other items that have been cleaned should be
stored in sealed plastic bags to prevent re-contamination.
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