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What concentration of hydrogen peroxide kills mold?


There are numerous articles online which claim that household 3% hydrogen peroxide can kill mold growing on household surfaces, yet I haven't managed to find scientific studies that show that. My question is what concentration of hydrogen peroxide is sufficient for killing household mold (defined usually as a reduction of 99% or some other number)?

I have tried searching online for studies regarding the efficacy of hydrogen peroxide in killing mold, and for the minimum concentration of hydrogen peroxide for killing mold, but I didn't manage to really find information on that, though I am not that skilled in finding such information and also don't have much access to scientific literature.


The CDC Guideline for Disinfection and Sterilization in Healthcare Facilities provides a good overview of various disinfectants and their effectiveness against different kinds of pathogens, along with citations if you're interested in more detail.

This document doesn't evaluate the effectiveness of Hydrogen Peroxide against Stachybotrys (black mold) specifically (the CDC specifically recommends Chlorine Bleach for this purpose), but it does describe it's effectiveness as a fungicide. Note that the level of disinfection needed to control pathogenic fungus in a healthcare setting is likely much higher than needed to control black mold in a house, but it can give you a sense of how effective Hydrogen Peroxide is overall:

A 0.5% accelerated hydrogen peroxide demonstrated bactericidal and virucidal activity in 1 minute and mycobactericidal and fungicidal activity in 5 minutes [656]

A 7% stabilized hydrogen peroxide proved to be sporicidal (6 hours of exposure), mycobactericidal (20 minutes), fungicidal (5 minutes) at full strength… [655]

The 7% solution of hydrogen peroxide, tested after 14 days of stress (in the form of germ-loaded carriers and respiratory therapy equipment), was… fungicidal (>5 log10 reduction in 20 minutes),[663]

A new, rapid-acting 13.4% hydrogen peroxide formulation (that is not yet FDA-cleared) has demonstrated sporicidal, mycobactericidal, fungicidal, and virucidal efficacy. Manufacturer data demonstrate that this solution sterilizes in 30 minutes and provides high-level

Commercially available 3% hydrogen peroxide is a stable and effective disinfectant when used on inanimate surfaces disinfection in 5 minutes [669]

From this, it seems like you'd want to use accelerated Hydrogen Peroxide, or 7% stabilize Hydrogen Peroxide to ensure fungicidal disinfection. 3% Hydrogen Peroxide is effective against bacteria, but the studies cited didn't test it against fungi.


Using Hydrogen Peroxide For Mold Removal

Hydrogen Peroxide has been used as a very simple and effective cleanser in our households for long. However, when it comes to mold removal at home, it can also become your best companion and make sure that the walls in your house don’t look bad. Molds are generally responsible for releasing a few toxic chemicals that might cause sneezing and allergy-like symptoms to the members of your household. Therefore, when only a small area of the house gets infected, using hydrogen peroxide can be a great way to get rid of the molds without having to spend hundreds of dollars on professional mold removal. Bellow we describe the method of removing mold with hydrogen peroxide, but if you want a safe and non-toxic/eco friendy cleaner we would recommend the mold removal products from our shop.

Hydrogen Peroxide For Mold Removal

It is important to understand that there is a difference between the commercially available bleach and the hydrogen peroxide we use at home. Bleach is generally harsher on the walls. Though peroxide can also result in the fading of the wall colors and must be diluted with water in order to be used safely, it is normally better than the use of bleach. It is easily available in the house. More importantly, you would not have to bear fumes and smells that are characteristic of bleach usage on the walls.

The first thing that you have to do here is to ensure your safety. Though hydrogen peroxide is safer, there is absolutely no harm in taking precautions to safeguard yourself. Wear gloves and breathing masks so that you remain safe. These mask and gloves will also protect you from getting infected by the mold when you are cleaning them from the walls. Therefore, you need to be very careful. Dilute the peroxide now. Ideally, the concentration should be only 25% with water which means that 3 parts water must be mixed with 1 part peroxide for better results. This would remove any chances of fading colors of the walls while still killing the mold.

Pour the solution into a spray bottle and then apply it thoroughly on the walls. Let the solution sit for at least 10-15 minutes, so that the chemicals get time to kill all the colonies of mold. After this is done, use a brush with very hard bristles to remove even the lightest debris on the walls. If there is any stain or debris left on the wall, then you would probably see new colonies in a very small time. Take your time in this process. Now, use some warm water to clean the walls and finally use paper towels or cleaning cloths to dry off the walls.


  • To remove mold, pour 3% concentration hydrogen peroxide into a glass spray bottle. This is the peroxide I use.
  • Spray the moldy surface completely so that the moldy areas are saturated with hydrogen peroxide.
  • Leave the surface to sit for 10 – 15 minutes while the hydrogen peroxide kills the mold. You want to wait until the peroxide has completely stopped bubbling and then give it an additional 5-10 minutes.
  • Scrub the area to make sure to remove all the mold and mold stains.
  • Wipe the surface down to remove residual mold and spores.

Don’t do it. Step away from the bottle. 35% hydrogen peroxide is far more caustic than it’s 3% counterpart. In addition, if it gets on your skin it will literally eat through it. Ask me about the time I poured 35% peroxide in my ear to stop an ear infection. Let’s just say my hearing is shot in that ear now and I will NEVER forget the pain I was in. My advice is to stick with the 3%. It works just as well with less risk.

If you do want to use a stronger peroxide solution, remediation companies often choose a 10% hydrogen peroxide solution. You can read more about how they use it in this great post.


How to use hydrogen peroxide to kill viruses

The typical 3% hydrogen peroxide concentration found in stores can be used as a disinfectant, or you can dilute it to a 0.5% concentration, which still has some effectiveness, using a mixture of 2.5 parts water and 0.5 parts 3% hydrogen peroxide.

Before disinfecting any surface with hydrogen peroxide, the CDC recommends using soap and water to clean the area. Once you've done so, you can pour or spray hydrogen peroxide on the surface and wipe with a paper towel or sponge.

After you've used hydrogen peroxide, make sure to leave it on the surface for at least one minute before drying to give it enough time to kill pathogens.

If you're cleaning with 3% hydrogen peroxide, use caution on some surfaces — such as countertops made of marble or granite — as its slight acidity can break down the finish of these surfaces over time. It can also cause discoloration, so test it out on a small spot of a colored surface before using it on a larger area.


Killing Mold With Vinegar And Hydrogen Peroxide

If you’re looking for effective ways to killing mold with vinegar and hydrogen peroxide, then our detailed guide will walk you through on how to do it correctly.

You have been hoping that this will be a night you won’t soon forget.

After all, you have put a lot of effort into this evening. Maybe you are looking to entertain a bunch of guests for a gala dinner party at your home. Maybe you are looking to throw the party of the century. Maybe you are preparing to have that special someone over for a romantic night in and dinner for two. Maybe you are more professionally-minded, and are looking to conduct some vital negotiations at your place of business. Whatever the case may be, you need everything to be absolutely perfect.

That’s a lot of pressure, but you’re up to it. You have spent weeks working to make this a perfect evening. You have spent your time preparing the decorations, ordering professional catering, maybe whipping up a thing or two on your own, and generally making sure that your space is as pristine as possible. It was a lot of hard work, but as your guests start to file in, thoroughly impressed, you can clearly see that it was all worth it.

Someone wrinkles their nose and asks what that unsavory-looking black spot is.

Maybe that spot is located up on your ceiling.

Maybe it’s present in the shower.

Maybe it’s attached to the walls.

To your horror, it might well be all three at once.

Wherever it is, you know what it is all too readily – mold.

Just like that, this has become an evening you won’t soon forget – but for all of the wrong reasons.

A mold infestation can wreak havoc on your life, as well as your property. Inhaling mold can be extremely dangerous, and its very presence is odious and extremely unpleasant. What is more, mold can, if left unchecked, be a deathblow for your property’s viability and value.

Mold infestations are a common problem for home and business owners. In particular, homeowners like to try and take matters into their own hands when it comes to mold removal. While larger infestations should ideally be dealt with by a team of trained professionals, if you “only” have a tiny outbreak on your hands, there are several home remedies you can employ to nip your mold problem in the bud.

Here are just a few such approaches you can take to remove mold on your own via vinegar, hydrogen peroxide, and other household items.

Why Is Cleaning Mold With Bleach A Bad Idea?

Let’s first look at how we can clean up mold with another common household item – bleach. This will be useful for comparing the effectiveness of our vinegar and hydrogen peroxide approaches later on.

That said, if you’re thinking “Why not simply mix the vinegar and bleach together, for double the mold-killing power,” don’t do that. Mixing the two together can create chlorine gas, and given that that’s the kind of thing that can get you in trouble in a war crimes court, it really isn’t the sort of thing you should be employing against mold spores, no matter how pernicious. This is, incidentally, one reason why so many people do prefer working with vinegar by comparison – the lower levels of danger and toxicity involved.

Using bleach to kill mold typically involves pouring a small quantity (one cup of bleach per one gallon of water with which you mix and dilute it) and then applying this to the surfaces in question.

How well does bleach fare against mold? Honestly, not very well. The bleach is not typically able to penetrate certain areas, such as wood, and so cannot effectively treat many surfaces affected by a mold outbreak. Add to that the potential for a slipup to lead to your permanently staining your home, and it should come as no surprise that vinegar and hydrogen peroxide are both far more well thought of as removal remedies.

Cleaning Mold With Vinegar And Hydrogen Peroxide

Cleaning with Vinegar

Now that we’ve established why something such as bleach is a generally bad idea for mold removal, let’s turn our attention back to vinegar. Like bleach, vinegar is a darling among the Do It Yourself home care crowd. It is something just about everyone owns and can easily be obtained. For our purposes, “vinegar” here refers to the type of white distilled vinegar you can typically get at the store.

So, how can you go about cleaning up mold with your Friendly Neighborhood Bottle of Vinegar?

To begin with, you’ll want to pour a certain amount of vinegar into a spray bottle. Since you are using a spray bottle to control the amount of vinegar used at a time, you don’t need to worry about how much is present. You’ll, thus, be able to spray the surface with your vinegar as much as needed. Be careful not to spray it so much that the spray starts to have an adverse effect on the surface itself. That being said, you also want to be sure that you are spraying enough to where there is an actual effect. While vinegar is certainly a safer overall option than bleach, there is no question that the latter is far stronger. As such, you are probably going to have to use more vinegar than you would bleach to get the job done. That being said, the safety factor and aforementioned ineffectiveness of bleach on certain substances still makes vinegar the superior choice in this regard.

After you have sprayed the surface in question, you will want to gently dab it and wipe it down with a rag. You’ll then want to wait about another 10 to 15 minutes and repeat the process. In between the spraying and dabbing, you’ll also want to have something on hand with which to scrape up and remove the mold in question if possible. That said, you want to make sure that this tool (whatever it may be for you) is not so abrasive as to damage the surface you are spraying and dabbing. Remember, one of the core reasons for using vinegar over other methods is the relative safety it provides with respect to preserving wooden finishes in particular.

Cleaning with Hydrogen Peroxide

Next, let’s turn our attention to cleaning up a moldy mess with hydrogen peroxide. For this, you’ll need both a bottle itself, as well as something with which to scrub the area in question. In terms of the amount you should be using, a 3% concentration of hydrogen peroxide should suffice, though for really stubborn mold you may need to go as high as 10%. From there, it is as simple and straightforward as was the vinegar – pour out a bit of hydrogen peroxide, dab it onto a cloth, apply it to the affected area, and then use something to scrub up the moldy remnants.

The Pros and Cons of Vinegar

There are many advantages to working with a vinegar mix. For one thing, as stated, vinegar is extremely easy to find. For another, vinegar is an all-natural cleaning agent. If you are into the “all-natural lifestyle” kick that is so popular nowadays, this is probably your preferred cleaning material overall, and it does its job well here. The natural acidity of vinegar makes it an ideal candidate for breaking down and, thus, helping to clear away pollutants, and the same holds true when it comes to how it treats mold.

The downside? Aside from that classic vinegar smell that accompanies its use, vinegar is not as strong as other cleaning products. That said, as demonstrated with the bleach, stronger is not always better, and vinegar is certainly more than up to the task of handling most mild to moderate mold outbreaks.

The Pros and Cons of Hydrogen Peroxide

How about hydrogen peroxide? It, too, is a pretty viable alternative in this respect. It is highly useful when it comes to cleaning up slightly more stubborn mold patches than might be assailable with vinegar. What is more, hydrogen peroxide, while nowhere near as common as vinegar, still isn’t too hard to find. In addition, hydrogen peroxide is an antibacterial agent, which is one reason you’ll typically see it used in hospitals. As such, if you want to make sure that you kill any bacterial agents along with the mold you’re treating, hydrogen peroxide can be a fantastic way to kill two birds with one stone.

The disadvantage? Mainly that it, again, is not as strong as bleach, and is slightly less available than vinegar. That being said, the advantages of hydrogen peroxide and vinegar over bleach in this respect have already been enumerated.

It’s worth noting that while vinegar and hydrogen peroxide are great solo artists when it comes to tackling mold problems, combined in the same container, they have serious chemistry problems – namely that they form a corrosive acid.

So, as with the vinegar/bleach mixture, that is something that you need to avoid.

That being said, there is no denying that, on their own, both vinegar, as well as hydrogen peroxide, serve as two of the most effective ways to clean up mold in a quick and effective fashion.


Clean and disinfect wet items

Be sure to put on a pair of latex gloves and goggles for protection before beginning your cleanup.

  • Disinfect non-porous materials: Wash glass, plastic and metal surfaces with a solution of equal parts hot water and 3% hydrogen peroxide** (found in supermarkets & drugstores). Scrub the solution into rough surfaces, such as concrete, with a stiff brush. Let the solution sit for 15 minutes and wipe dry.
  • Disinfect porous materials: Scrub porous surfaces such as wood and fabric with just the 3% hydrogen peroxide** (no additional water). Let the solution sit for 15 minutes and rinse clean. Leave non-porous materials to dry over several days and monitor for mold growth and odors. If mold develops, discard the item.

**Hydrogen peroxide is considered an &ldquooxygen bleach&rdquo. it is free from chlorine, but it can still discolor fabrics and other materials. As such, you may want to have a specialist handle items of sentimental or monetary value


What Are the Different Hydrogen Peroxide Concentrations?

Hydrogen peroxide (H2O2) differs from water (H2O) by the presence of an additional single atom of oxygen. Since the additional oxygen atom is "electron-loving," or electrophilic, hydrogen peroxide is a very powerful oxidizing agent. The added oxygen also makes hydrogen peroxide quite unstable, unless it is quite pure. Hydrogen peroxide is usually dissolved in water because of the danger of burns and contamination-induced instability associated with the pure form, and it is used at an appropriate dilution for the task at hand. There are a number of different hydrogen peroxide concentrations of commercial importance.

Hydrogen peroxide has an abundance of uses calling for a number of concentration levels, including uses as mouthwash, for soaking the feet, for cleaning fish aquariums and for the treatment of acne. It is also used in cleaning carpets, in polishing metals and to whiten paper products. Moreover, it is used in the laboratory, in sanitizing swimming pools and in wastewater treatment facilities. Included among the different hydrogen peroxide concentrations used are very high concentrations used for rocket fuel. In this regard, peroxide is used not only in rockets intended for outer space, but also for devices such as rocket belts for "inner space" that utilize a concentration of 90%.

Hydrogen peroxide dissolved in water is less of a safety issue. This becomes especially important at high concentrations, at which point catalytic peroxide decomposition can result in the formation of not only oxygen, but of dangerous steam. A much lower concentration of hydrogen peroxide is called for when used as mouth gargle, wound disinfectant or hair lightener. Such uses call for the lowest of the commercially different hydrogen peroxide concentrations — 3%. Even when that concentration is purchased, most dentists recommend a 50:50 dilution, bringing peroxide strength down to approximately 1.5%.

Slightly higher human-use peroxide concentrations may be available in some locations — 6% is readily available, for instance, in the UK. In the laboratory, the most commonly seen of the different hydrogen peroxide concentrations is 30%. Another commercially available grade is 35% — the so-called "food grade." The Food and Drug Administration (FDA), a US government agency, has decried the use of this product and recommends consumers not purchase 35% hydrogen peroxide for human use. Stronger concentrations for use as fuel can run as high as 98%.

The different hydrogen peroxide concentrations can all be produced in the same manner. Formerly, peroxide was produced by the electrolysis of sulfuric acid or some other, similar, sulfate material. In 2011, the anthraquinone process — a catalytic oxidation-hydrogenation process — is utilized.


3% hydrogen peroxide

I refer to the concentration “3%” a lot when I’m talking about peroxide. Even when I’m saying to dilute it further, I often refer to an amount of “3% hydrogen peroxide” to add to water.

Why 3%? Three percent is a familiar concentration, since the brown bottles at the drugstore are generally 3%. Maybe that is why I’ve gotten used to using 3% for examples, amounts and measurements.

Three percent also seems to be a “standard” of sorts. Because hydrogen peroxide is generally sold as 3%, many books, websites, and charts use 3% in examples, amounts, and formulas. I’ve just gotten used to 3% as a concentration.

Three percent is also what I mix and use in my home for most general everyday household purposes. There is no reason I have to do it this way – I could mix and use 5% instead. But I don’t. I mix and use 3%.

I keep a gallon bottle of 3% hydrogen peroxide in my kitchen. I use the 3% peroxide for a number of things without further dilution, and, of course, I also often further dilute it by mixing it into water. I also keep 3% in spray bottles, and containers, in my kitchen and bathroom.

But, there is no rule. If you use a lot of 1.5% peroxide as a mouthwash, you could keep a bottle of 1.5% peroxide in your bathroom.

Please BE SURE to clearly label all containers of peroxide with the concentration of peroxide they contain!


Hydrogen Peroxide and cell signaling, Part B

Ruben Quintana-Cabrera , Juan P. Bolaños , in Methods in Enzymology , 2013

Abstract

Hydrogen peroxide (H 2O2) is an important regulator of cell redox status and signaling pathways. However, if produced in excess, it can trigger oxidative damage, which can be counteracted by the antioxidant systems. Amongst these, the glutathione (GSH) precursor, γ-glutamylcysteine (γGC), has recently been shown to detoxify H2O2 in a glutathione peroxidase-1 (GPx1)-dependent fashion. To analyze how both γGC and GSH reduce H2O2, we have taken advantage of a colorimetric assay that allows simple and reliable quantification of H2O2 in the micromolar range. Whereas most assays rely on coupled enzymatic reactions, this method determines the formation of a ferric thiocyanate derivative after direct Fe 2 + oxidation by H2O2. Here, we detail the procedure and considerations to determine H2O2 reduction by both γGC and GSH, either from cell samples or in vitro reactions with purified enzymes from GSH metabolism.


Mold Cleaning Solutions

By Richard Driscoll

If you are a frequent reader of Cleanfax, you may remember an article I wrote titled “The Carolina Protocol.” It was the cover story of the June 2015 issue.

As someone who has worked in the restoration field and now teaches mold remediation, I am always seeking a lower-labor cost method of removing mold from surfaces, rather than the traditional methods of the past: Sanding, scraping, wire brushing, media blasting, etc.

The first lower-cost method I discovered was “blasting.” And while soda blasting and dry ice blasting have their place, and, if done correctly, do a really good job of removing mold, they also have some drawbacks.

When I discovered that hydrogen peroxide really works, as explained in “The Carolina Protocol” article, I thought we had finally found the best mold remediation process. The standard and guidelines in our industry describe the guiding principle of mold remediation as “mold removal,” but how the actual mold-removal process is performed is left up to the skilled technician.

As time moves on, other ideas and concepts come forward and must be considered, evaluated, and either accepted or discarded. In mold remediation, we now have two “cleaning” solutions that can be used for mold removal: Hydrogen peroxide and chlorine dioxide. This article looks at both solutions, comparing them to see which is better, or more appropriate, for our work.

Hydrogen peroxide

Hydrogen peroxide, which is an oxidizing agent, is the same solution that most people have at home in their medicine cabinet. We use it as a common antiseptic for small cuts. When used for mold remediation work, the concentration of the hydrogen peroxide is higher than what is in the medicine cabinet.

Thousands of mold remediation jobs have proven hydrogen peroxide to be an effective mold removal (not mold killing) cleaning product.

The benefits of hydrogen peroxide

  • It is an EPA-registered disinfectant with a very broad spectrum and very aggressive antimicrobial efficacy.
  • A good oxidizing agent, it can attack malodors and stains.
  • The odor is extremely mild and not offensive.
  • It does not generate environmentally objectionable byproducts.
  • If accidentally contaminated, it does not generate any hazardous gases. The decomposition products are water and oxygen.

Limitations of hydrogen peroxide

  • Solutions of hydrogen peroxide are not stable in sunlight, so packaging and storage are an issue.
  • It is capable of damaging certain textile dyes.
  • If contaminated, the container will undergo rapid pressurization with the risk of bursting.
  • Hydrogen peroxide has no bacteriostatic or fungistatic capability.
  • It is susceptible to degradation if contaminated therefore, containers and any water diluent must be very clean.
  • Peroxide is stable only under acidic conditions. As a result, it can damage surfaces that are not acid stable.

Chlorine dioxide

A more recent cleaning solution to arrive on mold remediation jobs is chlorine dioxide. Chlorine dioxide is a chlorine-based oxidizing agent that is somewhat like the well-known sodium hypochlorite, or standard chlorine bleach. Chlorine dioxide, however, has significant advantages over chlorine bleach.

First, for the chemists who may read this, chlorine dioxide, strictly speaking, is a gas at normal temperature and pressure. It is quite unstable and dangerous as a gas, so it is normally generated in water solution by a salt known as sodium chlorite. Please note that this is distinguished from table salt or sodium chloride. The “ite” versus “ide” suffix is important. For convenience, however, I’ll still refer to this item as chlorine dioxide.

Benefits of chlorine dioxide

  • It is an EPA-registered disinfectant that is active with a very broad spectrum and very aggressive antimicrobial efficacy. Of course, this substance can be a component of products that are not registered disinfectants, but, whether a product is Federal Insecticide, Fungicide, and Rodenticide Act registered, always follow label directions. Also keep in mind that our goal is to remove, not necessarily kill, the mold and associated spores.
  • A good oxidizing agent, it can attack malodors and stains.
  • Operates at mildly acidic pH conditions rather than the strong alkaline conditions required for chlorine bleach nevertheless, it is still effective over a wide pH range.
  • The odor is less objectionable than that of chlorine bleach.
  • It does not generate environmentally objectionable byproducts as would chlorine bleach.

Limitations of chlorine dioxide

  • Solutions of chlorine dioxide are not stable in sunlight, so packaging and storage are issues.
  • It is capable of damaging certain textile dyes.
  • It can produce toxic chlorine gas under certain conditions, especially if contaminated.
  • Chlorine dioxide has no bacteriostatic or fungistatic capability.
  • It is susceptible to degradation if contaminated therefore, containers and any water diluent must be clean.

Summary

We therefore have two mold removal cleaning solutions that work. Both are effective and have been proven effective in field use.

Which is the better product? Hydrogen peroxide and chlorine dioxide are almost totally equal in mold remediation effectiveness. But, in my own objective opinion, I would personally choose hydrogen peroxide, primarily because it does not leave any residual.

Richard Driscoll has a bachelor’s degree in mechanical engineering from Clarkson College of Technology, an MBA from the University of Dayton and is currently working on his doctorate. He is a professor at Webster University where he provides graduate and undergraduate level lectures. He is an IICRC Certified Master Restorer, Master Textile Cleaner and an approved instructor. Driscoll has been consulted by state governments on legislation related to the cleaning and restoration industry. He also is the author and instructor for Restoration Sciences Academy’s MR-110 and MR-210 microbial remediation classes and MR-211 trauma scene clean up class. He is IICRC approved instructor teaching WRT and AMRT. He can be reached at [email protected] .