The EPA publication,
A Brief Guide to Mold, Moisture, and Your Home
, is available here in
HTML and
PDF formats. This Guide provides information and guidance for
homeowners and renters on how to clean up residential mold problems and how to prevent
mold growth. A printed version will be available soon.
Biological Pollutants
in Your Home - This document explains indoor biological pollution,
health effects of biological pollutants, and how to control their growth and buildup.
One third to one half of all structures have damp conditions that may encourage
development of pollutants such as molds and bacteria, which can cause allergic reactions
-- including asthma -- and spread infectious diseases. Describes corrective
measures for achieving moisture control and cleanliness. This brochure was
prepared by the American Lung Association and the U.S. Consumer Product Safety Commission.
EPA Document Reference Number 402-F-90-102, January 1990.
Moisture control is the key to mold control, the Moisture Control Section from
Biological Pollutants
in Your Home follows:
Water in your home can come from many sources. Water can enter your home by leaking
or by seeping through basement floors. Showers or even cooking can add moisture
to the air in your home. The amount of moisture that the air in your home can hold
depends on the temperature of the air. As the temperature goes down, the air is
able to hold less moisture. This is why, in cold weather, moisture condenses on
cold surfaces (for example, drops of water form on the inside of a window). This
moisture can encourage biological pollutants to grow.
There are many ways to control moisture in your home:
- Fix leaks and seepage. If water is entering the house from the outside, your options
range from simple landscaping to extensive excavation and waterproofing. (The ground
should slope away from the house.) Water in the basement can result from the lack
of gutters or a water flow toward the house. Water leaks in pipes or around tubs
and sinks can provide a place for biological pollutants to grow.
- Put a plastic cover over dirt in crawlspaces to prevent moisture from coming in
from the ground. Be sure crawlspaces are well-ventilated.
- Use exhaust fans in bathrooms and kitchens to remove moisture to the outside (not
into the attic). Vent your clothes dryer to the outside.
- Turn off certain appliances (such as humidifiers or kerosene heaters) if you notice
moisture on windows and other surfaces.
- Use dehumidifiers and air conditioners, especially in hot, humid climates, to reduce
moisture in the air, but be sure that the appliances themselves don't become sources
of biological pollutants.
- Raise the temperature of cold surfaces where moisture condenses. Use insulation
or storm windows. (A storm window installed on the inside works better than one
installed on the outside.) Open doors between rooms (especially doors to closets
which may be colder than the rooms) to increase circulation. Circulation carries
heat to the cold surfaces. Increase air circulation by using fans and by moving
furniture from wall corners to promote air and heat circulation. Be sure that your
house has a source of fresh air and can expel excessive moisture from the home.
- Pay special attention to carpet on concrete floors. Carpet can absorb moisture and
serve as a place for biological pollutants to grow. Use area rugs which can be taken
up and washed often. In certain climates, if carpet is to be installed over a concrete
floor, it may be necessary to use a vapor barrier (plastic sheeting) over the concrete
and cover that with sub-flooring (insulation covered with plywood) to prevent a
moisture problem.
Moisture problems and their solutions differ from one climate to another. The Northeast
is cold and wet; the Southwest is hot and dry; the South is hot and wet; and the
Western Mountain states are cold and dry. All of these regions can have moisture
problems. For example, evaporative coolers used in the Southwest can encourage the
growth of biological pollutants. In other hot regions, the use of air conditioners
which cool the air too quickly may prevent the air conditioners from running long
enough to remove excess moisture from the air. The types of construction and weatherization
for the different climates can lead to different problems and solutions.
Your humidistat is set too high if excessive moisture collects on windows and other
cold surfaces. Excess humidity for a prolonged time can damage walls especially
when outdoor air temperatures are very low. Excess moisture condenses on window
glass because the glass is cold. Other sources of excess moisture besides overuse
of a humidifier may be long showers, running water for other uses, boiling or steaming
in cooking, plants, and drying clothes indoors. A tight, energy efficient house
holds more moisture inside; you may need to run a kitchen or bath ventilating fan
sometimes, or open a window briefly. Storm windows and caulking around windows keep
the interior glass warmer and reduce condensation of moisture there.
Humidifiers are not recommended for use in buildings without proper vapor barriers
because of potential damage from moisture buildup. Consult a building contractor
to determine the adequacy of the vapor barrier in your house. Use a humidity indicator
to measure the relative humidity in your house. The American Society of Heating
and Air Conditioning Engineers (ASHRAE) recommends these maximum indoor humidity
levels.
Outdoor Recommended Indoor Temperature Relative Humidity
+20 F. 35%
+10 F. 30%
0 F. 25%
-10 F. 20%
-20 F. 15%
Anne Field, Extension Specialist, Emeritus, with reference from the Association
for Home Appliance Manufacturers (
http://www.aham.org).