Got mold in your home? Here’s what to do.


As a heating, ventilation, and air conditioning contractor (HVAC contractor), we talk with clients every day about the importance of preventing mold with proper ventilation. In this article, you’ll find an overview of how to handle mold. We walk through the basics of mold cleaning and prevention. We also touch on the latest research regarding the health effects of mold exposure, so you have context for how seriously to take mold in your home. Please feel free to read through or jump to an area of interest:

What is mold?

There is always some mold everywhere – in the air and on surfaces all around us. Outdoors, molds play an important role breaking down dead organic matter like fallen leaves and dead trees. They reproduce by means of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air.

Mold may begin growing indoors when mold spores land on surfaces that are wet. There are many types of mold, and none of them will grow without water or moisture. Indoors, mold growth should be avoided because of the potential for structural damage to your home and negative effects on your health.

What are the health effects of mold?

In short, it depends. According the Centers for Disease Control and Prevention (CDC), some people have no apparent reaction to mold spores. But if you tend to have allergies, then you’re more likely to react to mold spores with allergic symptoms like stuffiness, throat irritation, coughing or wheezing, eye irritation, or in some cases, skin irritation. People with immune suppression or chronic lung disease may get serious infections in their lungs when exposed to mold.

In 2004, the Institute of Medicine (IOM) found limited or suggestive evidence linking indoor mold exposure and respiratory illness in otherwise healthy children. Other recent studies suggest a potential link of early mold exposure to development of asthma in some children, particularly among children who may be genetically susceptible to asthma development. Reducing mold spores at home seems to reduce the incidence of both allergies and asthma.

What about “toxic mold”? Certain molds are toxigenic, meaning they can produce toxins (specifically mycotoxins). According to the CDC, hazards presented by molds that produce mycotoxins are the same as other common molds that can grow in your home. There are relatively few reports of toxigenic molds found inside homes causing unique health conditions like memory loss or pulmonary hemorrhage (bleeding in the lungs). A cause-and-effect relationship between toxigenic mold and these unique conditions has not been established.

It’s worth reflecting on the elusive cause-and-effect relationship between mold and various health conditions. The reason is that molds and other fungi grow easily in damp indoor environments, which typically harbor plenty of other things that can make you sick, such as dust mites, bacteria, as well as chemicals, gasses, and particulate matter released from the materials on which molds are growing.

Should I test my home for mold?

It’s generally not necessary to identify the species of mold growing in a home. Current evidence indicates that allergies are the type of diseases most often associated with molds. Since the reaction of individuals can vary significantly either because of the person’s susceptibility or type and amount of mold present, sampling and culturing are not reliable in determining your health risk. If you’re susceptible to mold and mold is seen or smelled, there’s a potential health risk. No matter what type of mold is present, you need to remove the mold.

That said, there are a few situations when testing for mold is recommended:

  1. If your immune system is compromised, it’s a good idea to test for mold before buying or renting a new home.

  2. If you do not see mold in your home but have allergic reactions that are not clearly related to another cause (e.g. high pollen count in the spring), it’s worth testing for mold.

  3. If you expect to go to court over the mold in your home, you should get testing done to have a baseline for the type and amount of mold present.

  4. If you hire a professional to remediate mold in your home, you may want to test for mold afterwards to confirm that your home is free of mold.

For mold testing, clients have had positive experiences with Mold Testing Services of Oregon. Click here for a sample report. Diagnostic mold testing for a 1,500 square foot home costs about $600. A post-project test costs about $350.

What should I wear when removing mold?

Cleaning mold is generally a do-it-yourself project. But if the area covered by mold is more than 10 feet, you’ll probably want to consult a professional. In Portland, we find PureSpace to be both knowledgeable and trustworthy for mold remediation. Here’s what to wear if you decide to clean the mold yourself:

  • Wear a respirator. To limit your exposure to airborne mold, wear an N-95 respirator, available at most hardware stores. Some N-95 respirators resemble a paper dust mask with a nozzle on the front; others are made of plastic or rubber and have removable cartridges that trap most of the mold spores.

  • Use gloves. We recommend long gloves that extend to the middle of your forearm. When working with water and a mild detergent, ordinary household rubber gloves can be used. If you’re using a disinfectant, a biocide like bleach, or a strong cleaning solution, you should use gloves made from natural rubber, neoprene, nitrile, polyurethane or PVC. Avoid touching mold or moldy items with your bare hands.

  • Get goggles. It’s best to use goggles without ventilation holes.

  • Wash your clothes. As soon as you’re done cleaning mold, be sure to throw your clothes right in the washing machine. Any spores that may have settled on your clothes will get washed away.

How do I clean mold in my home?

In most cases, mold can be removed from hard surfaces with a thorough cleaning. Matt Ballou, President at PureSpace, recommends removing or covering porous surfaces, like beds or couches, with plastic before cleaning mold next to those surfaces. So for example, if you have a bed and rug next to a window with mold, it’s best to: (1) roll up the rug, (2) remove the bedding, and (3) cover the bed with plastic before cleaning the moldy window. The point is to prevent mold spores from spreading around your house during the cleaning process.

Thomas Nadermann with Mold Investigations recommends using a quaternary ammonium based cleaning product, like Fantastik All Purpose Cleaner. Never use bleach. Spray the moldy area with the cleaning product. Wait at least three minutes, then use a sponge or scrubbing brush to make sure to remove all the mold from the surface.

Absorbent or porous materials like ceiling tiles, drywall, and carpet may have to be thrown away if they become moldy. Mold can grow on or fill in the empty spaces and crevices of porous materials, so the mold may be difficult or impossible to remove completely.

How do I prevent mold from coming back?

If you clean mold without addressing the source of moisture that allowed the mold to spread, you can count on the mold coming back. That’s why preventing mold is all about moisture management. This isn’t a comprehensive list, but here are the things most homeowners should prioritize.

  • Plumbing leaks: Fix plumbing leaks as soon as possible. Dry all items completely.

  • Ducts: A surprising number of bathroom fans are not ducted outdoors. Rather, they channel the warm moist air from bathrooms into attics or side attics, causing mold to proliferate on roof sheathing. You’ll want to make sure your ducts direct air outdoors instead of back into your home. The best practice is to insulate your ducts to prevent condensation from building up.

  • Dehumidify: The CDC recommends that you keep humidity levels below 50% in your home all day long. So if you live in Portland, you should run a dehumidifier, especially if: (1) it’s the rainy season; (2) you dry clothes in your home; or (3) you live on a slope that directs water towards your home. Be sure to choose an ENERGY STAR certified dehumidifier, and rinse the air filter consistently (takes 5 minutes or less).

  • Ventilate: It’s critical to make sure you have proper air flow in your home - not so much that you have drafts or cold spots in the winter, but not little that you have a build up of mold or carbon monoxide. As a HVAC contractor, we consistently recommend the Panasonic WhisperGreen bath fan for improved ventilation.

Panasonic WhisperGreen Bath Fan

HVAC, ventilation, bath fan, panasonic whispergreen bath fan

Since we recommend and install this bath fan so often, it’s worth hitting a few highlights.

  • Efficient: The Panasonic WhisperGreen bath fan is the most efficient bath fan on the market. In 2018, it earned national recognition with the Most Efficient Award from ENERGY STAR.

  • Quiet: This is the quietest bath fan available. It’s soft operation is the most common comment we get from clients.

  • Automatic: This is the best part for mold prevention - it automates the entire process of controlling humidity in your home. When you go with the Panasonic Whispergreen Select, you can add on a condensation sensor that turns on the fan when humidity reaches a certain level. So you don’t need to do anything to make sure the air in your home is consistently below 50%, as recommended by the CDC. The fan makes it automatic.

How do I know I’m mold free?

  • You should have completed mold removal. Visible mold and moldy odors should not be present. Please note that mold may cause staining and cosmetic damage.

  • You must address the water or moisture problem before mold remediation can be considered finished.

  • People should have been able to occupy or re-occupy the area without health complaints or physical symptoms.

Special thanks to Matt Ballou with PureSpace, Garrett Dayfield with Mold Testing Services of Oregon, and Thomas Nadermann with Mold Investigations for their help researching this article. Mold Investigations is an industrial hygienist performing a wide range of sampling services for indoor air quality, including solvents, gases, asbestos and radon.

Bill Hoelzer