Does Steam Kill Mold: How To Use Steam To Kill Mold & Mildew

There are hundreds if not thousands of chemical-based products out there that promise to rid you of your mold and mildew problem for good, but what if you want to take a more natural route, one that’s more environmentally friendly?

Using steam to do the job might just be the answer, and in this article, we will be discussing how steam kills mold, how to use it effectively to clean your property, and what some of the drawbacks of this method may be.

So, to find out everything you need to know about using steam to kill mold, keep reading.

Does steam kill mold?

How does steam cleaning work?

Steam cleaning involves heating water past its boiling point of 100 degrees Celsius (212 Fahrenheit), to create high-temperature steam. This steam is then passed through a narrow tube to increase its pressure, producing a jet of hot steam that can kill mold and bacteria.

The combination of high heat, temperature, and pressure makes removing dirt and debris far easier, as it breaks down any adhesive properties of the grime you wish to remove.

The high temperature is also very effective at killing bacteria, dust mites, and many strains of fungi including mold and mildew.

How does steam kill mold?

The very high temperature that steam can reach (up to 149 Celsius, 245 Fahrenheit), is hot enough to kill mold, and despite some strains being able to produce heat-resistant spores, such as Byssochlamys fulva, they can only resist temperatures up to 100 Celsius or 212 Fahrenheit for a limited time before succumbing to it.

Steam cleaning mold will kill nearly all strains within a few seconds, but for heat-resistant strains, the steam should be applied for a minimum of 12 seconds in order to be certain it has been killed.

What is more effective, steam cleaning or mold-killing products?

Steam cleaning may at first appear to give you the kind of instant results you are looking for, however, if it is not used correctly, it may not actually rid you of a mold problem. In fact, it could even make the situation worse, as we will discuss later.

Using specifically designed mold-killing products, or even home remedies such as vinegar or hydrogen peroxide can on occasion be more effective, as the active ingredients will kill the mold and soak into the materials it is attached to, ensuring that all mold is killed, not only the visible growth on the surface.

Having said that, the benefit of using high-pressure steam is that it can reach difficult-to-reach areas, lacks the harsh chemicals of commercial products, and as long as the steam is applied for a minimum of 12 seconds on each patch of growth, should be sufficient to kill most strains.

Does steam kill all mold strains?

Steam will kill all mold strains as long as it is applied for long enough. In order to effectively kill all strains of fungi, steam must be applied directly to it for at least twelve seconds. This is because some strains have developed heat-resistant spores that can withstand temperatures up to 60 degrees. If these spores are not hit directly with the steam for this period of time, it may not be sufficient to kill them.

Even the most worrisome strains such as Stachybotrys chartarum (black mold), have the same structure as other mold and will just as easily be killed by the extreme temperatures steam can reach.

What surfaces and materials can you clean mold from with steam?

Steam is certainly a very useful weapon in the fight against mold, but as you will know, despite most of the vapor disappearing into the air, there is still some moisture left over once it has been used. This excess moisture can damage some materials and cause them to rot and deteriorate, so use the following list to determine which materials are safe to be steamed cleaned.

Materials and surfaces safe to be steam cleaned:

  • Countertops
  • Bathroom tiles (excluding marble)
  • Ceilings
  • Laminate and vinyl flooring
  • Bathroom and kitchen sinks
  • Toilets
  • Shower enclosures

Materials and surfaces not safe to steam clean:

  • Bamboo
  • Marble tiles
  • Drywall
  • Any walls decorated with water-based paint
  • Unsealed surfaces
  • Delicate materials such as silk
  • Absorbent materials such as carpets (unless your steam cleaner is specifically designed to clean them)

Which types of steam cleaners are best for killing mold?

Most steam cleaners have the ability to kill mold, however, for cleaning moldy carpets, a standard steam cleaner is not recommended, as carpet-specific units suck back up excess moisture, leaving them dry after being cleaned. A standard unit would leave excess moisture within the carpet, potentially causing additional mold growth.

Look for a unit that provides plenty of pressure (at least 65 psi (4.5 bar), and one that can keep a consistent temperature well above 100 degrees Celsius.

Below are some recommended models for steam cleaning mold off of bathroom tiles, work surfaces, and other flat nonabsorbant surfaces as well as units that are better suited to cleaning mold from carpets and absorbent materials.

How to kill mold using steam

Mold will be killed when it is exposed to high temperatures, but some strains will require exposure to steam for a longer amount of time. Use the following steps to effectively kill all strains of mold with steam.

Step 1. Purchase a quality cleaner with high-pressure nozzle attachments, and ensure it consistently heats water to 100 degrees and preferably has a wattage between 500 and 1,500 watts.

Step 2. Fill the tank with water and turn the unit on, waiting for it to reach temperature and begin producing steam.

Step 3. Position the nozzle a few inches away from the patch of mold you wish to remove. Gently move the nozzle over the area, ensuring it is exposed to the steam for at least 12 seconds before moving onto any other patches.

Step 4. Once you have steamed the area and allowed it to cool, use a clean cloth to wipe away any leftover mold or mildew residue.

Can using steam make a mold problem worse?

As discussed, steam can indeed be very useful in the fight against fungi, however, it is possible that if used incorrectly, steam has the potential to increase the amount of growth in your home, rather than decrease it.

Steam creates moisture and increases the amount of humidity within a room, two things that mold requires to live and grow. In fact, keeping the humidity level below 55% is one of the most common ways to fight mildew growth, as you are taking away one of its key components for life.

This is why it is essential to keep windows and doors open whilst you are using the cleaner, as well as ensure there is plenty of airflow to allow moisture-laden air to flow out of the room, rather than settling and being allowed to condense.

If you are concerned about high humidity and the potential worsening of fungal growth, it may be advisable to use a dehumidifier after you have steam cleaned to ensure the humidity level is decreased as quickly as possible.

Are there any other steps you should take after cleaning with steam to prevent further mold growth?

The main thing to consider after using steam to clean mold and bacteria from your home is to make sure all surfaces are as dried as possible as quickly as possible.

The easiest method is to of course wipe down any surfaces that have been treated with steam and remain wet. This should be done with a dry, clean towel and should only be attempted once the area has been given time to cool down, as the steam is very hot.

On summer days, opening windows and internal doors in your home or property will allow fresh, dry air to flow through each room, removing the moisture-laden air with it as it passes through.

For colder days, consider using a dehumidifier if opening windows is not an option. Internal doors should still be left open to allow as much airflow as possible.

Keeping the walls and surfaces as dry as possible will make it far less likely that mold and mildew will settle on the surfaces once again and begin to grow.

In newer-build properties, lack of airflow is a big problem due to them being heavily insulated and almost air-tight. Whilst this may help reduce heating costs, it results in stale, moisture-laden air staying within the property, which leads to mold and mildew growth. Installing passive ventilation vents or positive input ventilation units will help to reduce the overall humidity within a property.

There are also several mold-resistant paints you can use to cover troublesome areas, but ensuring there is adequate airflow should be the main focus before resorting to these measures.

When should a professional be called?

If several attempts at removing mold and mildew with steam yourself have resulted in new growth formation within a few weeks or months after treatment, you may have a larger humidity issue within your property.

Rising damp, leaking pipes, or poor ventilation can all contribute to mold infestation, and these are the sorts of things that mold remediation professionals will be able to investigate and remedy.

Dealing with mold by yourself on a regular basis can be a frustrating experience, not to mention the health hazards associated with fungal growth in homes, so if you find yourself suffering from this issue persistently, it may well be worth hiring a professional to assist you.


Steam can indeed kill mold, mildew, and bacteria on many types of surfaces within a property. Steam should be applied for a minimum of twelve seconds to ensure all strains are dead, and it should only be used on flat, non-porous surfaces. Rooms treated with steam should get as much airflow as possible after use to ensure the overall humidity stays lower than the 55% that fungi require.

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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