EPA 402-K-02-003: A Brief Guide to Mold, Moisture, and Your Home

Reading notes

A2Z's reading notes on this document, in its order. They are not the document's own wording; check figures against the original before relying on them.

Key Messages

The key to mold control is moisture control. If mold is a problem in your home, clean up the mold and fix the water problem. Dry water-damaged areas and items within 24-48 hours to prevent mold growth.

Mold Basics

Why is mold growing in my home? Molds are part of the natural environment. They reproduce by releasing tiny spores that float through the air. Mold begins growing indoors when spores land on wet surfaces. No type of mold will grow without water or moisture.

Can mold cause health problems? Molds produce allergens, irritants, and in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mold may cause allergic reactions — hay fever-type symptoms (sneezing, runny nose, red eyes, skin rash). Mold can trigger asthma attacks and irritate the eyes, skin, nose, throat, and lungs of both allergic and non-allergic individuals.

How do I get rid of mold? It is impossible to eliminate all mold spores indoors — some spores are always present. Mold spores will not grow if moisture is absent. If mold is present, clean it up AND fix the water problem. If you clean up mold but do not fix the moisture problem, mold will almost certainly return.

Mold Cleanup

Who should do the cleanup? Less than 10 square feet: In most cases, you can handle the job yourself. More than 10 square feet: Consult the EPA guide Mold Remediation in Schools and Commercial Buildings. HVAC contamination: Do not run the HVAC if you suspect mold — it can spread spores throughout the building. Sewage or contaminated water: Call a professional. Health concerns: Consult a health professional before starting cleanup.

Cleanup guidelines: Fix plumbing leaks and water problems promptly. Scrub mold off hard surfaces with detergent and water. Porous materials like ceiling tiles and carpet may need to be discarded. Do not paint or caulk moldy surfaces — clean and dry first.

What to Wear When Cleaning Moldy Areas

N-95 respirator (must fit properly). Long gloves extending to mid-forearm. Goggles without ventilation holes.

How Do I Know When Remediation Is Finished?

The water or moisture problem must be fixed. Visible mold and moldy odors should not be present. No signs of water damage upon re-inspection. People should be able to occupy the area without health complaints. This is ultimately a judgment call.

Moisture and Mold Prevention Tips

Moisture control is the key to mold control. When water leaks or spills occur indoors, act quickly — if wet materials are dried within 24-48 hours, mold will generally not grow. Clean and repair roof gutters regularly. Make sure the ground slopes away from the building foundation. Keep AC drip pans clean and drain lines clear. Keep indoor humidity below 60% (ideally 30-50%). Act quickly if you see condensation on windows, walls, or pipes.

To reduce humidity: Vent dryers and stoves to outside. Use AC and dehumidifiers. Run bathroom fan when showering. Use exhaust fans when cooking.

To prevent condensation: Increase ventilation. Cover cold water pipes with insulation. Increase air temperature.

Renters: Report all plumbing leaks and moisture problems immediately to your building owner or manager.

Testing or Sampling for Mold

In most cases, if visible mold growth is present, sampling is unnecessary. No EPA or federal limits exist for mold or mold spores. Surface sampling may be useful to determine if an area has been adequately cleaned. Sampling should be conducted by professionals and analyzed per AIHA or ACGIH methods.

Hidden Mold

You may suspect hidden mold if a building smells moldy but no visible source can be found. Common hidden locations include behind drywall, wallpaper, or paneling; under ceiling tiles; under carpets and pads; inside walls around pipes; inside ductwork; and in roof materials above ceiling tiles. Investigating hidden mold requires caution — disturbing mold sites can release large numbers of spores. Consider hiring an experienced professional.

Cleanup and Antimicrobials

Antimicrobials are not recommended as a routine practice during mold cleanup. In most cases, it is not possible or desirable to sterilize an area — a background level of spores will remain but will not grow if the moisture problem is resolved. If antimicrobials are used, always ventilate the area. Do not mix cleaning products, as toxic fumes can result.

Dead mold may still cause allergic reactions — it must be removed, not just killed.

Additional Resources

For more information visit: www.epa.gov/mold

EPA 402-K-02-003 — This document presents recommendations. EPA does not regulate mold or mold spores in indoor air.