Module 2 of 7 · Beginner · 8 minutes
Mold Basics
Learn how to tell if it is mold, what it means for your health, and how to clean a small patch safely or know when to hire help.
What You Will Be Able to Do
- Tell mold from dirt, stains and look-alikes
- Explain why color does not tell you how harmful a mold is
- Clean a patch under about 10 square feet with the right gear
- Decide which moldy belongings to clean and which to throw out
- Know when testing is worth paying for and when it is not
Lesson 1
Is It Really Mold
Many spots that look like mold are something else. A white crust on concrete that dissolves in water is usually mineral salt. Dark lines along ceiling joists are often dust. A simple test helps. Put a drop of diluted bleach on the spot. Mold and mildew lighten within a minute or two. Dirt does not.
Whatever the spot turns out to be, check for dampness. A moisture reading near the spot tells you more than the color does. Mold only grows where things stay wet.
Key Points
- Mold lightens under a drop of diluted bleach, dirt does not
- White crust that dissolves in water is usually mineral salt
- A damp surface is the real problem to solve
Lesson 2
Moisture Is the Real Cause
Mold spores are everywhere, indoors and out. They only grow when they land on something that stays damp. That is why killing mold is never the goal. Fixing the water is.
Leaks, high humidity and condensation on cold surfaces are the usual causes. If you clean mold without fixing the moisture, it comes back, often within weeks.
Key Points
- Spores are everywhere, moisture decides where they grow
- Fix the leak or humidity before you clean
- Mold that returns fast points to a moisture source you missed
Lesson 3
Black Mold and Your Health
Many common molds are black, and color does not tell you how harmful a mold is. The CDC advises treating all indoor mold the same way. Fix the moisture and remove the growth safely.
Most healthy people have mild or no reactions to small amounts of mold. Infants, older adults and people with asthma, allergies, lung disease or a weak immune system are more at risk. They should stay away from cleanup and see a doctor if symptoms start or get worse.
Key Points
- Color does not show whether a mold is more harmful
- Treat all indoor mold the same way
- Vulnerable people should never do mold cleanup
Lesson 4
The 10 Square Foot Line
The EPA treats about 10 square feet as the line for DIY mold cleanup. That is roughly a 3 by 3 foot patch. Under that size, a careful homeowner can usually handle it. Over that size, or if mold is inside walls or ducts, bring in a specialist.
In New York State, mold jobs over 10 square feet need a licensed mold assessor and a separate licensed remediator. Other places have their own rules, so check before you start a large job.
Key Points
- About 10 square feet, a 3 by 3 foot patch, is the DIY line
- Mold in walls, ducts or large areas is a pro job
- New York State requires licensed pros over 10 square feet
Lesson 5
How to Clean a Small Patch
Wear an N95 respirator, goggles without vent holes and long gloves. Close the room off and put a fan in a window blowing out. Scrub hard surfaces with detergent and water, then dry them fully.
Moldy drywall, ceiling tile and insulation cannot be scrubbed clean. Cut them out, bag them in heavy plastic and seal the bags before you carry them through the house.
Key Points
- N95, vent-free goggles and long gloves at a minimum
- Detergent and water on hard surfaces, then dry fully
- Moldy porous building materials get cut out and bagged
Lesson 6
What You Can Save
Hard, nonporous items like metal, glass, solid wood and hard plastic can almost always be cleaned and kept. Washable clothes usually come back with hot water and a second wash.
Soft items with mold growing inside them are a different story. Mattresses, pillows and foam cushions usually cannot be saved. Photograph and list everything before you throw it out, in case you file a claim.
Key Points
- Hard items clean up, soft stuffed items usually do not
- Wash clothes hot and twice
- Photograph and list items before you toss them
Lesson 7
When Testing Makes Sense
If you can see mold, you usually do not need a test. Fix the water and remove the growth. Testing earns its cost when mold is hidden, when you need proof a job was done right, or when a landlord, buyer or insurer needs evidence.
Store petri dish kits almost always grow something, because spores are everywhere. They prove very little. If you do test, hire an assessor who does not also sell the removal work.
Key Points
- Visible mold rarely needs a test
- Store dish kits prove very little
- Use an assessor who does not sell the removal
Small Mold Cleanup Checklist
Check What You Learned
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