A BRIEF GUIDE TO

MOLD,

MOISTURE,

AND

YOUR HOME
This Guide provides

information and guidance

for homeowners and

renters on how to clean

up residential mold

problems and how to

prevent mold growth.

EPA 402-K-02-003

U.S. Environmental Protection Agency

Office of Air and Radiation

Indoor Environments Division

1200 Pennsylvania Avenue

Mailcode: 6609J

Washington, DC 20460

www.epa.gov/iaq
1

Contents Page

Mold Basics

Why is mold growing in my home? 2

Can mold cause health problems? 2

How do I get rid of mold? 3

Mold Cleanup

Who should do the cleanup? 4

Mold Cleanup Guidelines 6

What to Wear When Cleaning Moldy Areas 8

How Do I Know When the Remediation

or Cleanup is Finished? 9

Moisture and Mold Prevention and Control Tips 10

Actions that will help to reduce humidity 11

Actions that will help prevent condensation 12

 Testing or sampling for mold 13

Hidden Mold 14

Cleanup and Biocides 15

Additional Resources 16

A BRIEF GUIDE TO MOLD,

MOISTURE, AND YOUR HOME
MOLD BASICS

 hy is mold growing in my home? Molds are part of the

natural environment. Outdoors, molds play a

part in nature by breaking down dead organic

matter such as fallen leaves and dead trees, but

indoors, mold growth should be avoided. Molds

reproduce by means of tiny spores; the spores

are invisible to the naked eye and float through

outdoor and indoor air. Mold may begin growing

indoors when mold spores land on surfaces that

are wet. There are many types of mold, and none

of them will grow without water or moisture.

Can mold cause health problems? Molds are usually not a

problem indoors, unless mold spores land on a wet or

damp spot and begin growing. Molds have the potential to

cause health problems. Molds produce allergens

(substances that can cause allergic reactions), irritants, and

in some cases, potentially toxic substances (mycotoxins).

Inhaling or touching mold or mold spores may cause

allergic reactions in sensitive individuals. Allergic responses

include hay fever-type symptoms, such as sneezing, runny

nose, red eyes, and skin rash (dermatitis). Allergic reactions

to mold are common. They can be immediate or delayed.

Molds can also cause asthma attacks in people with asthma

who are allergic to mold. In addition, mold exposure can

irritate the eyes, skin, nose, throat, and lungs of both mold2

■ The key to mold control is moisture control.

■ If mold is a problem in your home, you should clean up

the mold promptly and fix the water problem.

■ It is important to dry water-damaged areas and items

within 24-48 hours to prevent mold growth.

W

Mold growing outdoors on

firewood. Molds come in

many colors; both white and

black molds are shown here.
3

allergic and non-allergic people. Symptoms other than

the allergic and irritant types are not commonly

reported as a result of inhaling mold.

Research on mold and health effects is ongoing. This

brochure provides a brief overview; it does not describe

all potential health effects related to mold exposure. For

more detailed information consult a health

professional. You may also wish to consult your state or

local health department.

How do I get rid of mold? It is impossible to get rid of

all mold and mold spores indoors; some mold spores

will be found floating through the air and in house dust.

The mold spores will not grow if moisture is not

present. Indoor mold growth can and should be

prevented or controlled by controlling moisture

indoors. If there is mold growth in your home, you

must clean up the mold and fix the water problem. If

you clean up the mold, but don’t fix the water problem,

then, most likely, the mold problem will come back.

Magnified mold spores.

Molds can gradually

destroy the things

they grow on. You can

prevent damage to

your home and

furnishings, save

money, and avoid

potential health

problems by

controlling moisture

and eliminating mold

growth.
4

Who should do the cleanup? Who should do the cleanup

depends on a number of factors. One consideration is the

size of the mold problem. If the moldy area is less than

about 10 square feet (less than roughly a 3 ft. by 3 ft. patch),

in most cases, you can handle the job yourself, following the

guidelines below. However:

■ If there has been a lot of water damage, and/or mold

growth covers more than 10 square feet, consult the U.S.

Environmental Protection Agency (EPA) guide: Mold

Remediation in Schools and Commercial Buildings.

Although focused on schools and commercial

CLEANUP

If you already have a

mold problem –

ACT QUICKLY.

Mold damages what it

grows on. The longer

it grows, the more

damage it can cause.

Leaky window – mold is beginning to

rot the wooden frame and windowsill.

MOLD
5

buildings, this document is applicable to other

building types. It is available free by calling the EPA

Indoor Air Quality Information Clearinghouse at

(800) 438-4318, or on the Internet at:

www.epa.gov/iaq/molds/mold_remediation.html.

■ If you choose to hire a contractor (or other professional

service provider) to do the cleanup, make sure the

contractor has experience cleaning up mold. Check

references and ask the contractor to follow the

recommendations in EPA’s Mold Remediation in Schools

and Commercial Buildings, the guidelines of the American

Conference of Governmental Industrial Hygenists

(ACGIH), or other guidelines from professional or

government organizations.

■ If you suspect that the heating/ventilation/air

conditioning (HVAC) system may be contaminated with

mold (it is part of an identified moisture problem, for

instance, or there is mold near the intake to the system),

consult EPA’s guide Should You Have the Air Ducts in Your

Home Cleaned? before taking further action. Do not run

the HVAC system if you know or suspect that it is

contaminated with mold - it could spread mold

throughout the building. Visit www.epa.gov/iaq/pubs/

airduct.html, or call (800) 438-4318 for a free copy.

■ If the water and/or mold damage was caused by sewage

or other contaminated water, then call in

a professional who has experience cleaning and fixing

buildings damaged by contaminated water.

■ If you have health concerns, consult a health professional

before starting cleanup.
6

Tips and techniques The tips and techniques presented in this

section will help you clean up your mold problem.

Professional cleaners or remediators may use

methods not covered in this publication. Please note

that mold may cause staining and cosmetic damage. It

may not be possible to clean an item so that its

original appearance is restored.

■ Fix plumbing leaks and other water problems as

soon as possible. Dry all items completely.

■ Scrub mold off hard surfaces with detergent and water,

and dry completely.

Places that

are often or

always damp can be hard to maintain completely

free of mold. If there’s some mold in the shower or

elsewhere in the bathroom that seems to reappear,

increasing the ventilation (running a fan or opening

a window) and cleaning more frequently will usually

prevent mold from recurring, or at least keep the

mold to a minimum.

Bathroom Tip

MOLD CLEANUP GUIDELINES

Mold

growing

on the

underside

of a plastic

lawnchair

in an area

where

rainwater

drips through

and deposits

organic

material.
■ Absorbent or porous materials, such as ceiling tiles and

carpet, may have to be thrown away if they become

moldy. Mold can grow on or fill in the empty spaces and

crevices of porous materials, so the mold may be

difficult or impossible to remove completely.

■ Avoid exposing yourself or others to mold (see

discussions: What to Wear When Cleaning Moldy Areas

and Hidden Mold.)

■ Do not paint or caulk moldy surfaces. Clean up the

mold and dry the surfaces before painting. Paint applied

over moldy surfaces is likely to peel.

■ If you are unsure about how to clean an item, or if the

item is expensive or of sentimental value, you may wish

to consult a specialist. Specialists in furniture repair,

restoration, painting, art restoration and conservation,

carpet and rug cleaning, water damage, and fire or water

restoration are commonly listed in phone books. Be

sure to ask for and check references. Look for specialists

who are affiliated with professional organizations.

7

Mold growing

on a piece of

ceiling tile.
8

■ Avoid breathing in mold or mold spores. In order

to limit your exposure to airborne mold, you may want to

wear an N-95 respirator, available at many hardware

stores and from companies that advertise on the

Internet. (They cost about $12 to $25.) Some N-95

respirators resemble a paper dust mask with

a nozzle on the front, others are made primarily

of plastic or rubber and have removable cartridges that

trap most of the mold spores from entering.

In order to be effective, the respirator or mask

must fit properly, so carefully follow the instructions

supplied with the respirator. Please note that the

Occupational Safety and Health Administration (OSHA)

requires that respirators fit properly (fit testing) when

used in an occupational setting; consult OSHA for more

information (800-321-OSHA or osha.gov/).

WHAT TO WEAR WHEN

CLEANING

MOLDY AREAS

Mold growing on a suitcase stored in a

humid basement.

It is important

to take

precautions to

LIMIT

YOUR

EXPOSURE

to mold and

mold spores.
9

How do I know when the remediation or cleanup

is finished? You must have completely fixed the

water or moisture problem before the cleanup or

remediation can be considered finished.

■ You should have completed mold removal. Visible mold

and moldy odors should not be present. Please note that

mold may cause staining and cosmetic damage.

■ You should have revisited the site(s) shortly after

cleanup and it should show no signs of water damage

or mold growth.

■ People should have been able to occupy or re-occupy the

area without health complaints or physical symptoms.

■ Ultimately, this is a judgment call; there is no easy

answer. If you have concerns or questions call the

EPA Indoor Air Quality Information Clearinghouse

at (800) 438-4318.

■ Wear gloves. Long gloves that extend to the middle of

the forearm are recommended. When working with water

and a mild detergent, ordinary household rubber gloves

may be used. If you are using a disinfectant, a biocide

such as chlorine bleach, or a strong cleaning solution,

you should select gloves made from natural rubber,

neoprene, nitrile, polyurethane, or PVC (see Cleanup

and Biocides). Avoid

touching mold or moldy

items with your bare hands.

■ Wear goggles. Goggles

that do not have

ventilation holes are

recommended.

Avoid getting mold or

mold spores in your eyes. Cleaning while wearing N-95

respirator, gloves, and goggles.
10

■ When water leaks or spills occur

indoors - ACT QUICKLY.

If wet or damp materials or areas

are dried 24-48 hours after a leak

or spill happens, in most cases

mold will not grow.

■ Clean and repair roof gutters regularly.

■ Make sure the ground slopes away from the building

foundation, so that water does not enter or collect

around the foundation.

■ Keep air conditioning drip pans clean and the drain

lines unobstructed and flowing properly.

MOISTURE AND MOLD

PREVENTIONAND

CONTROL TIPS

Moisture

Control is the Key to

 Mold Control

Mold growing

on the surface

of a unit

ventilator.
11

■ Keep indoor humidity low. If

possible, keep indoor

humidity below 60 percent

(ideally between 30 and 50

percent) relative humidity.

Relative humidity can be

measured with a moisture or

humidity meter, a small,

inexpensive ($10-$50)

instrument available at many

hardware stores.

■ If you see condensation or moisture collecting on

windows, walls or pipes - ACT QUICKLY to dry the

wet surface and reduce the moisture/water source.

Condensation can be a sign of high humidity.

Actions that will help to reduce humidity:

 Vent appliances that produce moisture, such as

clothes dryers, stoves, and kerosene heaters to the

outside where possible. (Combustion appliances

such as stoves and kerosene heaters produce water

vapor and will increase the humidity unless vented

to the outside.)

 Use air conditioners and/or de-humidifiers

when needed.

 Run the bathroom fan or open the window when

showering. Use exhaust fans or open windows

whenever cooking, running the dishwasher or

dishwashing, etc.

Condensation on the inside of a

windowpane.
12

Actions that will help prevent condensation:

 Reduce the humidity (see preceeding page).

 Increase ventilation or air movement by opening doors

and/or windows, when practical. Use fans as needed.

 Cover cold surfaces, such as cold water pipes, with

insulation.

 Increase air temperature.

Mold

growing

on a

wooden

headboard

in a room

with high

humidity.
Renters: Report all plumbing leaks and moisture problems

immediately to your building owner, manager, or

superintendent. In cases where persistent water

problems are not addressed, you may want to contact

local, state, or federal health or

housing authorities.

13

Testing or sampling for

mold Is sampling for mold

needed? In most cases, if visible

mold growth is present, sampling

is unnecessary. Since no EPA or

other federal limits have been set

for mold or mold spores, sampling

cannot be used to check a

building’s compliance with federal

mold standards. Surface sampling

may be useful to determine if an

area has been adequately cleaned or remediated. Sampling

for mold should be conducted by professionals who have

specific experience in designing mold sampling protocols,

sampling methods, and interpreting results. Sample

analysis should follow analytical methods recommended by

the American Industrial Hygiene Association (AIHA), the

American Conference of Governmental Industrial Hygienists

(ACGIH), or other professional organizations.

Rust is an indicator that condensation

occurs on this drainpipe. The pipe should

be insulated to prevent condensation.
14

Suspicion of hidden mold You may suspect hidden mold if a

building smells moldy, but you cannot see the source,

or if you know there has been water damage and residents

are reporting health problems. Mold may be hidden in

places such as the back side of dry wall, wallpaper, or

paneling, the top side of ceiling tiles, the underside of

carpets and pads, etc. Other possible locations of

hidden mold include areas inside walls around pipes

(with leaking or condensing pipes), the surface of walls

behind furniture (where condensation forms), inside

ductwork, and in roof materials above ceiling tiles (due

to roof leaks or insufficient insulation).

Investigating hidden mold problems Investigating hidden mold

problems may be difficult and will require caution when the

investigation involves disturbing potential sites of mold

growth. For example, removal of wallpaper can lead to a

massive release of spores if there is mold growing on the

underside of the paper. If you believe that you may have a

hidden mold problem, consider hiring an experienced

professional.

HIDDEN MOLD

Mold growing

on the back

side of

wallpaper.
Cleanup and Biocides Biocides are substances that can destroy living

organisms. The use of a chemical or biocide that kills

organisms such as mold (chlorine bleach, for example) is

not recommended as a routine practice during mold

cleanup. There may be instances, however, when

professional judgment may indicate its use (for example,

when immune-compromised individuals are present). In

most cases, it is not possible or desirable to sterilize an

area; a background level of mold spores will remain - these

spores will not grow if the moisture problem has been

resolved. If you choose to use disinfectants or biocides,

always ventilate the area and exhaust the air to the

outdoors. Never mix chlorine bleach solution with other

cleaning solutions or detergents that contain ammonia

because toxic fumes could be produced.

Please note: Dead mold may still cause allergic reactions in some

people, so it is not enough to simply kill the mold, it must

also be removed.

15

Water stain

on a basement

wall — locate

and fix the

source of the

water promptly.
For more information on mold related issues including

mold cleanup and moisture control/condensation/humidity

issues, you can call the EPA Indoor Air Quality Information

Clearinghouse at

(800) 438-4318.

Or visit:

www.epa.gov/iaq/molds

16

ADDITIONAL RESOURCES

Mold growing on fallen leaves..

This document is available on the Environmental Protection Agency, Indoor

Environments Division website at: www.epa.gov/iaq/molds/moldguide.html
Acknowledgements

EPA would like to thank Paul Ellringer, PE, CIH, for providing the photo on page 14.

Please note that this document presents recommendations. EPA does not regulate

mold or mold spores in indoor air.

NOTES