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The decision to clean and remove mold
depends on many factors. In general, visible mold growing on surfaces
where people may come in contact with it should be cleaned and removed.
The most important objective in any mold
cleaning is to eliminate or repair the source of moisture. Even
if a building is stripped of all components and every spore is killed
or removed, normal background mold spores from outdoors or on replacement
parts have the potential to grow if there is sufficient moisture
available.
In a vast majority of cases, mold problems
in homes are related to flooding or water leaks that affect many
materials in the structure, including lumber. Drying the wood products
exposed to moisture is an important first step in cleaning mold.
In most climates, this drying will occur naturally once any standing
water is removed. Providing air flow around the wood will encourage
faster drying.
Mold growth cannot be supported on wood
dried to below 20 percent moisture content. Lumber used in construction
will typically dry to below 20 percent moisture content before the
structure is enclosed.
The amount of mold present and the likelihood
of it being disturbed should be considered when determining whether
to clean mold. In some cases, wood can simply be treated for mold
growth with a bleach solution, then dried and enclosed.
The process of removing mold from enclosed
spaces could increase exposure to mold spores in the short term.
High indoor mold spore counts are sometimes found when walls and
floors containing mold are opened and disturbed.
Cleaning small amounts of mold from wood
is relatively straightforward. Mold removal becomes more complex
when there are heavy amounts of mold on a majority of the lumber
or if the building has been in service for some time and the mold
originated from leaks into the building cavity. In these instances,
mold clean up should be done by a professional cleaning and restoration
company.
When cleaning any mold, basic personal
protection equipment such as rubber gloves, eye protection and a
high-quality pollen or dusk mask should be worn.
The molds seen on lumber are largely
a collection of fungal spores on the surface of the wood. Wet wiping
and scrubbing the lumber will remove the mold. But simply wiping
the wood can release spores into the surrounding air. A better approach
is to gently spray or wet down the mold prior to removal.
There are a number of products on the
market, ranging from common bleach to commercial mildewcides, which
are promoted for cleaning mold from wood. However, the U.S. Environmental
Protection Agency suggests using a mild detergent and water for
most mold clean up. The EPA recommends wet vacuuming the area, wiping
or scrubbing the mold with detergent and water and, after drying,
vacuuming with a high-efficiency particulate air (HEPA) vacuum.
Common bleach and water can be used for
cleaning mold. The U.S. Centers for Disease Control (CDC) recommends
using a solution of 10 parts water to one part bleach to clean mold
from surfaces.
Stronger formulations of bleach and water
may be used, particularly to remove the discoloration caused by
the mold fungi. The Wood Handbook, published by the U.S.
Forest Products Laboratory, recommends a solution of one part household
detergent, 10 parts bleach and 20 parts warm water. The solution
should be applied using a bristle brush or sponge to scrub the surface
of the wood.
When using bleach indoors, make sure
there is adequate ventilation and wear personal protection equipment.
Never mix bleach with ammonia or any detergent or cleansers that
contain ammonia.
If commercial products are used for cleaning
mold, be sure to follow the manufacturer's instructions for use.
You can find additional information about
mold online at these sites:
Mold, Housing and Wood
Western Wood Products Association
www.wwpa.org/lumberandmold.htm
A Brief Guide to Mold, Moisture and Your Home
U.S. Environmental Protection Agency (EPA)
www.epa.gov/iaq/molds/moldguide.html
Questions and Answers about Stachybotrys chartarum
and Other Molds
U.S. Centers for Disease Control (CDC)
http://www.cdc.gov/mold/stachy.htm
Common Questions and Answers About Mold and Wood-Based
Products
U.S. Forest Products Laboratory
www.fpl.fs.fed.us/rmmn/rmmn--moldqa.html
Also, see the other Fast Facts on mold and
wood products in this series:
No. 1 - What is Mold?
No. 2 - Preventing and Controlling
Mold
No. 3 - Cleaning Mold on Wood
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