After the Storm: A Calm Guide to Cleaning Up Mold

This is a researched explainer, drawn from the sources listed below. It contains no affiliate links. It is general information based on public agency guidance, not professional, medical or safety advice for your home.

In South Florida, the storm is often the short part. What follows is a few days of heat, standing water and air so humid it seems to sit on the furniture. Mold needs only moisture and time, and after a hurricane it has plenty of both. The good news is that the guidance from the EPA and the CDC is clear, and most of it comes down to speed, ventilation and good judgment.

First, safety before cleanup

Before any cleaning, make sure the house is safe to enter and the power situation is under control. If you are running a generator, it belongs outdoors only, never in the house, garage or carport, and at least 20 feet from doors, windows and vents, because of the risk of carbon monoxide ¹⁰. The U.S. Consumer Product Safety Commission lists the symptoms of carbon monoxide poisoning as headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion, and advises that if you suspect it, you get outside to fresh air immediately and then call 911 ¹².

Not everyone should take part. Florida's Department of Health has advised that people with weakened immune systems, mold allergies, asthma or other chronic lung disease should not clean or remove moldy materials ¹¹. If you or anyone in your household falls into one of these groups, talk to your doctor and consider bringing in help.

The 24-to-48-hour window

Time matters more than any product. The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth ². Wood, drywall, carpet and upholstered furniture that stay wet are where trouble usually starts.

The CDC is equally plain about what to do if you miss the window. If your home and its contents could not be dried within 24 to 48 hours, assume you have mold growth ⁷⁹. Anything that was wet with floodwater and cannot be cleaned and dried completely in that time should be thrown away or moved outside ⁹.

In practice, that means opening the house up as soon as it is safe, moving wet rugs and upholstered pieces out of the way, and running fans to keep air moving.

Bring the humidity down

Drying the surfaces is half of it. The air is the other half. The EPA recommends keeping indoor relative humidity below 60 percent, ideally between 30 and 50 percent if possible ³. In a Palm Beach September, that rarely happens on its own.

Once power is restored, air conditioning and dehumidifiers do the heavy lifting. An inexpensive hygrometer, a small humidity meter, lets you watch the number fall rather than guess. Mold control, as the EPA puts it, depends on moisture control ².

What to keep, and what to let go

Hard surfaces, such as tile, glass, metal and sealed stone, can generally be cleaned and kept ¹. Porous, absorbent materials are another matter. Floodwater and mold can penetrate deep into soaked, porous materials, which is why the EPA advises sorting materials and throwing away anything you cannot clean and dry ⁴.

The items most often lost after flooding include ¹⁴⁹:

• carpet and carpet padding
• upholstered furniture and mattresses that were soaked
• drywall and insulation that were wet
• ceiling tiles
• paper goods, books and cardboard

For valuable or sentimental pieces, such as documents, photographs, art and fine textiles, the EPA suggests consulting a specialist rather than discarding them in a hurry ¹.

Protect yourself while you work

The CDC recommends, at a minimum, a NIOSH-approved N95 respirator, protective gloves (non-latex, vinyl, nitrile or rubber), and goggles that give complete eye protection ⁷⁹. Goggles with open vent holes will not keep out dust and small particles ⁹. Long sleeves and clothes you can wash right away are sensible additions.

Work in short stretches, keep windows open where possible, and take breaks outside. If you begin to feel unwell while cleaning, stop and talk to your doctor.

Cleaning: soap first, bleach with care

For hard surfaces, the EPA's approach is simple: scrub mold off with detergent and water, then dry completely ¹. The agency does not recommend bleach or other biocides as a routine part of mold cleanup, noting that a background level of spores will always remain, that they will not grow once the moisture problem is resolved, and that dead mold can still cause allergic reactions in some people, so it must be removed, not just killed ⁶.

If you do use bleach, the CDC's rules are firm ⁸⁹:

• Never mix bleach with ammonia or any other cleaner. The combination can produce dangerous fumes.
• Use no more than 1 cup of household bleach per 1 gallon of water.
• Never use bleach straight from the bottle.
• Open windows and doors for fresh air, and wear the protective gear above.

On porous materials, no cleaner reliably reaches mold growing beneath the surface. That is why the guidance favors removal over scrubbing ⁴.

When to call a professional

The EPA's rule of thumb is useful. If the moldy area is less than about 10 square feet, roughly a 3-foot by 3-foot patch, in most cases you can handle the job yourself. If there has been a lot of water damage, or mold covers more than 10 square feet, the EPA points to its guide Mold Remediation in Schools and Commercial Buildings, which applies to homes as well ¹.

Call in help, too, if:

• the water was contaminated by sewage, which the EPA says calls for a professional experienced with contaminated water ¹
• the HVAC system or ductwork may be contaminated; the EPA advises not running it if you know or suspect mold inside ¹
• you smell mold but cannot see it, since mold can grow out of sight behind walls and under floors
• anyone in the household has health concerns about the exposure

If you hire a contractor, the EPA advises choosing one with experience in mold cleanup, checking references and asking them to follow EPA guidance or that of recognized professional groups ¹.