Mold questions, answered plainly

A persistent musty smell, past water damage, peeling or bubbling paint, and warped floors are common clues. The EPA notes hidden mold can grow on the back of drywall, under carpet pads, inside ductwork, and above ceiling tiles. An inspection with moisture readings is the usual next step.

The EPA says that for moldy areas smaller than about 10 square feet, in most cases you can do it yourself: scrub hard surfaces with detergent and water, dry completely, and wear gloves, goggles, and an N-95 respirator. Larger areas, sewage, a lot of water damage, or suspected HVAC contamination call for professional guidance.

The EPA does not recommend biocides like bleach as a routine practice in mold cleanup, and notes that dead mold can still cause allergic reactions, so it must be removed. Never mix bleach with ammonia-containing cleaners.

If mold is visible, the EPA says sampling is usually unnecessary. Testing helps with hidden mold, documentation for buying, selling, or renting, and confirming a cleanup worked.

The EPA says that if wet materials are dried within 24 to 48 hours after a leak, in most cases mold will not grow. After that, assume hidden materials need checking.

The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. A small hygrometer shows where you stand.

No. The EPA advises against painting or caulking moldy surfaces; clean up the mold and dry the surface first. Paint over mold is likely to peel.

It depends on the policy and the cause. Mold resulting from a sudden covered event, like a burst pipe, is often treated differently from mold caused by long-term leaks or humidity. Read your policy and report losses promptly.

Under California Health and Safety Code 17920.3, visible mold growth that endangers occupants, as determined by a health officer or code enforcement officer, makes housing substandard, and the owner must correct it. Notify your landlord in writing first.

It varies with how much material is removed, drying time, and whether testing and rebuild are included. Ask for a written schedule with your estimate.

Compare the moisture fix, containment and negative air, which materials are removed, HEPA cleaning, drying, verification or clearance testing, and whether rebuild is included. For rebuild work, check the contractor's license at cslb.ca.gov.

We review it and connect you with an independent mold remediation company serving your city, which contacts you to arrange an inspection and written estimate. Requesting an estimate doesn't commit you to anything.