Does Bleach Kill Mold?

If you have a problem with mold in your home, then you know it is not a pleasant experience. Not only is mold unsightly, but it can also cause health problems for you and your family. So, when you discover mold, you want to get rid of it as quickly as possible.

As a solution, many homeowners reach for bleach. But does bleach permanently kill mold on porous surfaces like drywall or hardwood floors? It is a common question we get from our clients. To set the record straight, United Water Restoration Long Island CEO Phil DePaul asks NYS licensed Mold Assessor and trusted partner, David Roberts, owner of Roberts Environmental Corp.


What is Mold?

First things first, let us talk about what mold actually is. Mold is a natural part of the environment; you can find it anywhere, indoors and outdoors. It is a pesky—and sometimes dangerous—fungus that thrives in damp, warm areas. Often in homes, it is found in bathrooms, basements, attics, and crawl spaces because these areas are typically more humid than the rest of the house. Moisture can come from leaks in pipes, condensation, or flooding.

Once mold starts growing, it can spread quickly. Mold reproduces by releasing tiny spores into the air. These spores are invisible to the naked eye and can travel through the air until they land on a new surface and begin to grow and reproduce, creating more mold.

In this video, Dave says to think of mold as a plant. The seed you put in your garden needs moisture in order to grow. With proper conditions, it will grow roots, and a sprout will pop out of the ground. Similarly, mold begins as a microscopic organism (the seed), and its hyphae, or roots, grow within a material. It then colonizes and becomes visible. The process can happen relatively quickly – 24 to 48 hours in a moisture-filled environment.

“Mold starts as a microorganism, very small, you won’t see it with the naked eye. With the right condition—moisture and temperature—it’s going to create these multicellular strands called hyphae in a substrate, for instance, drywall or wood, any porous building material,” says David. “The mold begins to reproduce by sending spores into the air, which can land on other surfaces, and again if the conditions are right, those spores can begin to colonize, and the process starts over again.”

Not only does mold look unpleasant, but it also breaks down the material it’s growing on. And the longer it’s left untouched, the more damage it does, and its presence can result in extensive structural damage. Mold is also a known allergen and can produce toxins that affect our health, especially those who are immunocompromised.

The Truth about Bleach and Mold

Now that we know what mold is and how it grows, let’s answer the question: does bleach kill mold or hide it? While there are countless websites touting bleach as mold kryptonite, we are here to debunk that myth.

Bleach can kill mold on non-porous surfaces like tile and glass. However, bleach cannot penetrate porous surfaces like wood and drywall. So, if you have mold growing on a porous surface in your home – bleach will not do the trick.

The Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) no longer recommend bleach for killing mold. Bleach contains 90% water. And guess what? Mold loves water! When applied, the chlorine cannot penetrate the surface and quickly evaporates, leaving a considerable amount of water behind. This water often soaks into the porous surface, allowing the mold to flourish.

“Even though the surface may look cleaner,” David says, “the hyphae root system is absorbing that extra water and growing more, getting stronger, and often returns worse than before.”

“And you risk disturbing the mold and sending spores into the air and you’re dealing with bleach which is a volatile organic compound,” he adds.”

Mold on the walls

The Dangers of Using Bleach to Remove Mold

Homeowners are lead to believe that since chlorine-based bleaches are useful for cleaning and disinfecting, it’s going to be effective at removing mold. But both the EPA and OSHA say the use of a chemical or biocide, such as chlorine bleach, is not recommended as a routine practice during mold cleanup. Not only will mold spores remain, but when misapplied or mixed with other substances, bleach can be dangerous to humans and pets. This is why you should never use common household bleach for mold removal.

  • You will disturb the mold, sending toxic spores into the air. Inhaling them can cause allergic reactions and respiratory symptoms. Bleach will also make your mold problem worse.
  • Harmful fumes exacerbate health issues like asthma and other respiratory conditions and can irritate your eyes, mouth, throat, and skin.
  • Bleach is corrosive that discolors and breaks down surfaces over time. It can weaken wood and damage metal finishes.
  • Mixing bleach with other household cleaners such as ammonia products creates a hazardous asphyxiant gas called chloramine. Exposure causes irritation to the eyes, nose, throat, skin, or respiratory tract. Symptoms include coughing, shortness of breath, chest pain, watery eyes, and nausea.

Many people think that using bleach is the best way to remove mold. However, this is simply not true. It’s best to leave it to the professionals who specialize in mold remediation.

What Should I Do To Kill Mold?

The bottom line: when it comes to mold removal, steer clear of bleach! So, if you discover mold in your Long Island home, what should you do? The answer is simple: call the professionals.

Mold abatement is not a DIY project; it requires specialized knowledge and equipment and the use of safe and effective methods. If the area is greater than 10 square feet, NYS guidelines require a mold assessor and remediator to be involved. Leave it to United and Roberts Environmental—we’ll take care of everything for you, from inspection and assessment to cleanup and prevention.

“If you have mold in your home, the best thing to do is call a NYS licensed mold assessment firm like Roberts Environmental or a NYS licensed mold remediation contractor such as United Water Restoration of LI. We work together to give Long Islanders peace of mind and a healthy environment,” says Phil.

Technicians remediating mold instead of using bleach.

When you make the call, you can expect

Initial Consultation: We will ask questions about your home and health. This information helps us determine the extent of the problem and develop an action plan.

On-Site Inspection: A specialist arrives to do a visual examination of your property and damaged areas. They look for signs of mold growth and water damage and sample the air and surfaces to test for mold spores. These samples are sent to a laboratory for analysis.

Report Findings & Propose Work Plan: Based on the results of the inspection and laboratory tests, we prepare a detailed report of the findings. This report includes a list of recommendations for remediation.

Set Up, Clean Up, and Restoration: Mold remediation is a technical process. You need professionals who have the experience and expertise to do the job safely and effectively.

Does My Homeowners Insurance Cover Mold?

Now you may be wondering if your homeowners insurance will cover the cost of remediation. The answer depends on the cause of the mold and how your policy specifies coverage. Be sure to check with your insurance provider to see what is and isn’t covered under your policy. And, if you’re not sure what caused the mold in your home, it’s best to have a professional take a look to determine the source of the problem.

If you have homeowners insurance, you may be protected if the mold is the result of a covered event, such as a burst pipe. However, if the mold is due to your own negligence, such as not properly ventilating an area prone to moisture, your policy is unlikely to cover the cost of remediation.

Many policies underwritten in New York that have mold riders also have a cap, or sublimit, of coverage on fungus damage – we can help you understand those Policy Declaration pages.

Phil DePaul and David Roberts headshots.

To Sum Up

If you think you have mold in your home, avoid using chlorine bleach, and don’t try to remediate it yourself—you could end up doing more harm than good. Consult with the professionals at United Water Restoration at (631) 494-4764 and Roberts Environmental at (631) 562-8440. We work together to assess damaged areas, develop a remediation plan, and help you take steps to prevent future growth. Let us know how we can help you get rid of the mold in your home and restore it back to its original condition.

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