Does Mold Fogging Work: And Does It Actually Stop Mold?

Dealing with a mold infestation can be a difficult and frustrating problem, especially if you thought you had dealt with the issue, only to find them constantly returning after a few weeks or months.

This is why some people consider mold fogging as a solution to the problem. However you may have questions like, how does it work, which types are best, is it safe and are there more effective methods out there?

In this article, we answer all these questions and more, so for all you need to know about mold fogging, keep reading.

Does mold fogging work

What is mold fogging?

Mold fogging (also called misting), is a process whereby either a small mechanical unit (called a fogger) or a pressurized can (called a bomb), releases an antimicrobial spray into the air to kill airborne spores and to reach areas of the home that are otherwise inaccessible or impossible to treat by more traditional methods. It is preferable to find fogging solutions that are non-toxic and biodegradable and are approved by the Environmental Protection Agency (EPA) as this is not always the case.

How is it supposed to work?

The units (or bombs) are set up around the property, usually in the most heavily affected areas (such as attics or basements), and the fumes are released through the property.

Upon contact with mold, mildew, or their airborne spores, the chemicals prevent the fungi’s ability to convert nutrients into energy, essentially starving it and halting its growth and spread. Some chemicals also break down the cell functions of the fungi, killing it outright.

What different types of fogging are there?

There are two types of fogging available, wet and dry. Dry fogging involves using aerosolized disinfectant chemicals to spread through a property, killing mold on contact as we have already discussed, whereas wet fogging involves adding small amounts of water to the solution in order to create larger droplets.

Dry fogging still creates moisture droplets of course, but these have a diameter between 10-15 microns, whereas the added water utilized in wet fogging creates droplets with a significantly larger diameter of between 20-30 microns.

Dry fogging is usually the preferred method, as wet fogging can add to high moisture levels within a property, which can exacerbate or even create new mold and mildew issues.

Is it effective?

The efficacy of mold fogging is a difficult question to answer, as it certainly is effective for killing mold and its spores. However, the main issue with this method of remediation is that once the fungi is killed, it is not removed, and will still need to be removed once the fogging is complete.

The reason that the fungi cannot simply be left is that despite being dead, the spores and fungi can still cause allergic reactions if they were to be inhaled or come into direct contact with a person’s skin that is sensitive to them. This may prevent its further growth, but it does not make it any safer to have on your property.

The other issue, is that mold and mildew have grown in your property for a specific reason. There were adequate nutrients available for it and there was also the correct level of humidity and moisture. Fogging will certainly kill the mold that had previously grown, but it has done nothing to address the root cause of the problem.

It is highly likely that once the fogging is complete if nothing further is done to lower humidity levels and increase the airflow within the property, you will see mold, mildew, and fungal growth continue.

Does fogging kill mold spores?

The chemicals used within mold bombs and foggers certainly can kill mold spores, even those that are airborne. This is one of the benefits of this method of remediation and one that other methods (such as using mold and mildew-killing sprays) will usually miss.

The spores are often one of the most frustrating aspects of dealing with a fungal infestation, as while you are dealing with an affected patch of wall for example, the disturbed spores will travel through the room and property, setting up new colonies wherever the environment is suitable for them.

It is therefore understandable that you would assume killing all spores within the air would resolve the issue, but unfortunately, this is not the case.

There are always fungal spores in the air, so as soon as this treatment is complete, the spores that are currently within your property will indeed be killed, but they will quickly be replaced. This is again why tackling the core issue is vital to rid your property of mold over the longer term.

Is mold fogging safe?

Fogging is generally considered safe if the products used are non-toxic and biodegradable, however, antimicrobials are sometimes used which can be more hazardous to health.

In either case, fogging should never be conducted when any individuals are on the property, and it must be left vacant for a minimum of half an hour, with some products requiring the rooms to be left for between two to four hours after fogging.

If setting up a mold “bomb”, ensure you wear protective equipment such as a breathing mask and eye protection, whilst following the instructions on the canister carefully.

Even chemicals that are generally considered to be safe whilst in liquid form (such as hydrogen peroxide), can become dangerous when turned into a fine mist. So mold fogging does have the potential to be dangerous if the correct precautions are not taken.

How long does it take?

The amount of time mold fogging takes depends greatly on the square footage of the property you are treating. Small rooms can be completed within a few hours, whereas whole properties that are badly affected by fungal growth may take several days to treat.

To give an example of timeframes, If treating a single room with a mold bomb, the treatment would take 2-3 hours, with a further 30 minutes or up to two hours (depending on the product) required to leave the room vacant after treatment has finished. This would give an overall time of roughly 3.5 to 5 hours to treat a single room with a mold bomb.

What should you cover when using a mold fogger?

The concentrations that either hydrogen peroxide or Concrobium are found in mold foggers are often not high enough to damage fabrics or hard surfaces. However, products that contain antimicrobials and pesticides may damage carpets and other soft furnishings.

It is for this reason that to be entirely sure that you are protecting the goods within the property being treated, you should cover anything of value with tarps or plastic sheeting of some kind for protection.

If possible, remove all electronics from the room being treated, as high moisture levels may affect its circuitry and could damage the product.

What to do after fogging for mold

After fogging has been completed and you have waited the suggested amount of time for the fumes to settle and clear, you can return to the room or rooms that have been treated.

As stated earlier in this article, the spores and mold may now be dead, but can still cause allergic reactions, so they must be removed.

A HEPA (high-efficiency particulate air filter) vacuum cleaner is best suited to the job and will be able to remove and contain the ultra-fine spores. This will remove the dead spores, but the root cause of the problem should now also be addressed.

From this point on, it is important that you complete a thorough inspection of the property to check for leaks, high humidity levels, or any other source of moisture that may be attracting mold and mildew.

If you are struggling to find the cause of the infestation, hiring a mold remediation expert will save a lot of time, as they are well aware of the most likely causes and should be able to source the issue fairly promptly and advise accordingly.

What are more effective methods of whole-house remediation?

The most effective method of whole home mold remediation is to call a professional or a team of professionals to inspect, assess, and treat your property.

Trying to find the source of moisture that is drawing mold back to your property time after time can be frustrating and time-consuming. You may not even be able to find it at all if the problem lies underground or in an inaccessible area. This is where the experts come in.

Professionals will have dealt with home mold infestation many times before and therefore will have a wealth of understanding of the most likely causes and locations for mold to be growing.

After assessing your property, the remediation experts will find the root cause of the infestation and create an action plan on how to tackle it.

The most important aspect of this is that they will not only look to kill the fungi that are already present, like mold fogging does, but will kill it, and remove the source of moisture that is allowing it to return time after time. Finding and removing the source is the only true way to completely remove mold from a property that is badly infested.

How much does dry fog mold removal cost?

If you have already dealt with the cause of mold growth in your home by increasing ventilation, fixing broken pipes or leaks, and want to quickly kill the remaining mold, then you can, of course, use a fogger to do so quickly, just remember that you’ll still need to clean up the dead fungi afterward.

In the US, a mold fogger can be rented from most hardware stores for around $20 for 24 hours, with the chemicals (Concrobium for example) costing around $150 for one gallon. So the treatment can be completed for less than $200 in total. Using a mold bomb may be the cheaper option depending on the square footage of the area you need to treat, as one mold bomb will cost around $60.

In the U.K., these prices are fairly similar, with mold foggers costing around £40 per day and Concrobium costing £90 (on average) per gallon. A single mold fogger bomb however is often priced at around £12 per canister.

Are DIY foggers safe and effective?

As long as you wear the correct safety equipment whilst using either mold bombs or foggers, and use them exactly as stated on the product themselves, they should indeed be safe to use. Making sure you are using them when no one else is on the property is vitally important, as is leaving plenty of time after the treatment is complete to allow the fumes to dissipate.

The efficacy remains debatable, as we have discussed that these methods should only be used once the root cause of the infestation has been discovered and rectified, otherwise, you will continue to see the same problem again.

How often to test for mold

Once you have completed your fogging treatment, it is important to test your property regularly to ensure that the problem remains under control. This should be conducted at least once per month if the risk factors in your area are low, and once every quarter in high-risk areas (such as high humidity locations).

How to test for mold

Mold testing can be completed easily with DIY kits at home that can be ordered online. The best kits come with swabs that you gently rub against any areas you suspect may be growing fungi, then send off to a lab to have professionally tested.

You can also buy tests that monitor the number of mold spores in the air. There are pre-determined acceptable levels of spores that you would expect to find in any property, these tests will assess the number on your home and will determine if there is an unacceptable amount as a result of new growth.

If you are unsure about going down the DIY route, you can also hire expert mold inspectors who will conduct a thorough examination of the property, including testing mold spore levels, although this is obviously the more costly option.


Mold fogging on its own will only kill the fungi that are presently on your property but does not address the underlying cause of the infestation. For fogging to be successful, you must first find and resolve the reason for its growth, then fogging can be used to kill what has already grown. It’s important to remove the dead mold once fogging is complete, as it can still cause allergic reactions in those susceptible.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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