Ask an Expert: Can spraying chemicals remove mold?

Ask an Expert is an occasional feature where we pose a question submitted by readers to our Healthy Home Director Carl Grimes and Healthy Building Scientist Joe Medosch. We cover topics such as professional mold removal, clean air practices, healthy home tips, etc.

Reader Question: Can the mold and water damage in my home be remediated safely and correctly by just spraying chemicals?

This is a common question, and the short answer is no because professional mold removal is a better option. Mold removal methods must be effective at removing the mold, safe for the occupants of the house, and not cause unintended consequences later. Chemical sprays and other mold treatments do not meet these criteria. While the execution can be complicated, the basics of mold remediation are quite simple and must be done in this order:

  1. Completely stop the moisture that is causing the mold to grow.
  2. Contain and physically remove the mold either by cleaning or removal/replacement of the affected surface as outlined in the scope of work by a certified professional.
  3. Confirm the work was fully completed with an independent assessment and/or testing.

These steps should be outlined by a professional, certified as a mold assessor or in mold removal, and are based on the ANSI IICRC S500 Professional Standard for Water Damage and the ANSI IICRC S520 Professional Standard for Mold Remediation. ANSI (American National Standards Institute) recommendations are based on solid, well-documented science and represent the closest thing to a federal standard in existence.

In most states, mold remediators have no oversight and are not required to follow ANSI or any other standards. If you are hiring someone to do mold remediation, we strongly recommend finding a professional mold removal that’s certified and will provide a written guarantee that the ANSI 500/520 standard will be followed.

Several key points of the ANSI Standards are especially critical for consumers to understand. Read our notes on professional mold removal:

Products that are EPA Registered

You may notice some chemical sprays with an “EPA Registered”.  All products affecting micro-organisms (including mold) are required by federal law to have a registration number and approved label from the EPA. However, this does not mean that the EPA or any organization has independently validated product claims or safety. It just means that the products have ingredients that could be hazardous or harmful, so they are legally required to be registered. Many of these chemicals are not tested for health effects on humans.

The Use of Bleach on Mold Growth

Lastly, we want to address the use of bleach on mold. Using bleach on visible mold growth is NOT recommended by either the EPA or the CDC and is not part of the ANSI-IICRC S520 Standard for Professional Mold Remediation. First, bleach is a chemical and can impact people with chemical sensitivities especially if used in areas that are not well ventilated. Second, on non-porous surfaces such as tile, bleach is no more effective at removing mold than a damp cloth and a mild detergent, so we recommend the least toxic option.

Also, since bleach is mostly water, on porous surfaces, such as wood or drywall, the water in the bleach is easily absorbed by the material. So, while you may have wiped off or discolored the surface mold to the point that you can’t see it, you’ve actually provided plenty of water to regrow and possibly spread the mold beneath the surface.

Final Note

Because we are not aware of peer-reviewed studies that assess the efficacy and safety of methods of mold treatment, including coatings and chemical sprays which do not meet the standard for “removal”, we do not currently recommend them. However, we are open to all information and would be happy to review new practices and products with independent third-party studies.


Meet Our Experts:

Carl Grimes – Carl has both the personal experience of how an unhealthy home created his own disabling health issues, plus professional experience in various industries working in the Indoor Air Quality (IAQ) field. Carl also wrote Starting Points for a Healthy Habitat in 1999, detailing possibilities of what could occur in a house to make its occupants sick, how to identify what was happening, and what to do about it.

Joe Medosch – Joe has almost 30 years of experience as a contractor and 10 years as a master trainer with expertise in home performance, particularly in health and energy-efficiency. His proficiency includes building science & diagnostics and Indoor Air Quality (IAQ) assessments. He has served on numerous committees developing industry standards including RESNET Standard 380, Equipment Sub-Committee, and BPI multifamily standards development.

Still got more questions about mold? Click here. To learn more about additional conditions in your home that may be impacting your health, take the Hayward Score survey today! Get suggestions on how to make your home healthier, as well as detailed, personalized Action Plans to get you started.

Getting to a healthy home can seem daunting, but it is possible and our experts are here to help! You can Ask an Expert, and one of our Hayward Score team members will get back to you.

How useful was this post?

Click on a star to rate it!

Average rating 4.4 / 5. Vote count: 8

No votes so far! Be the first to rate this post.

Ready to Improve the Health of your Home?

Hayward Score helps you discover how your home may be impacting your health in minutes – – for FREE!

Answer a quick set of questions then get a personalized list of action items. Transform your home and health today!

Related Articles


Our guide on indoor quality will help you diagnose possible issues and implement intelligent solutions to improve the quality of the air inside your home.

Related Articles