Why 24 to 48 hours
Mold needs moisture and something to eat. Drywall paper, wood framing, carpet backing and dust are all food. Give them water and the clock starts. EPA's advice is to dry water damaged areas and items within 24 to 48 hours to prevent growth. CDC says that if you could not dry within that window, assume there is mold.
What speeds it up
- Warmth. Water left standing breaks down faster when it is warm, and a closed valley house in summer stays warm.
- Humidity. EPA says keep indoor humidity under 60 percent, ideally 30 to 50. A wet room pushes it well past that.
- Hidden water. Inside walls, under flooring and above ceilings, where no air moves.
- Porous materials. Paper faced drywall and insulation hold water against food.
Signs mold is already growing
- A musty smell, especially in closets, behind washers and under sinks
- Spots that look fuzzy or speckled, gray, green or black
- Paint bubbling or staining that spreads
- Sneezing, runny nose, red eyes or skin rash in some people, which EPA lists as common reactions
What to do right after a leak
Stop the water
Main valve, then call a plumber.
Get standing water out
Extraction, not just fans.
Remove soaked porous material
Carpet pad, wet insulation, soft drywall.
Dry with equipment
Air movers and a dehumidifier sized to the room.
Read until dry
Wet areas must match a dry room in the same house.
If mold already started
EPA sizes cleanup by area. Under about 10 square feet, most people can do it with gloves, goggles and an N-95. From 10 to 100 square feet, limited containment. Over 100, full containment. Porous material with mold, like drywall and insulation, is removed, not painted over. CDC says never mix bleach and ammonia and use no more than 1 cup of bleach per gallon of water. People with asthma, allergies or a weak immune system should not do the cleanup.
Does turning off the AC cause mold?
Turning the AC off in a closed house in summer raises indoor humidity and heat, which helps mold. During a dry out, follow the restorer's plan. And EPA says do not run an HVAC system you know or suspect has mold in it.