Does Heat Kill Mold? A Closer Look at This Controversial Method


Mold is a common problem in homes that can not only damage your possessions and home itself, but also lead to some serious health issues if inhaled or exposed to the skin. Understandably, homeowners want to get rid of mold as quickly and thoroughly as possible when discovered. This has led some to try using heat as a DIY mold killing solution before calling in professional mold remediation services.

But does applying heat really kill and eliminate mold effectively? While heat can help halt the spread of mold growth, it has some limitations that are important to understand. This article takes a science-based look at using heat treatment for mold removal, including its effectiveness on different materials, risks involved, and tips for the best results.

Does Heat Kill Mold

How Does Heat Affect Mold Growth?

Before diving into the practical use of heat on mold, it helps to understand how temperature impacts mold itself. The key factors include:

Mold Grows Best at Moderate Temperatures and Humidity

Mold growth thrives in damp conditions between around 40-100°F. This makes heat alone insufficient to prevent mold, as humidity and moisture levels also play a crucial role.

High Heat Can Deactivate Mold Growth

Exposing mold to temperatures above 160°F can damage the proteins and structures within the mold, deactivating its ability to grow and reproduce. However, mold is not completely eliminated.

Heat Alone Does Not Kill Mold Entirely

High heat may stop active mold growth, but does not kill all mold on a molecular level or destroy its root structures and spores. This means mold can often return once ideal growing conditions are present again.

Effectiveness Depends on Multiple Factors

How well heat treatment works depends on the temperature reached, length of exposure, mold species, material/surface infected, and depth of growth. Results can vary widely.

Can You Really Kill Mold with a Clothes Dryer?

A commonly asked question is whether running moldy items through a hot dryer cycle can kill off the mold for good. Here’s a look at how effective this method really is:

Dryers May Get Hot Enough to Deactivate Mold

Typical home dryers can reach internal temperatures between 130-135°F. Some dryers with sanitize or allergen cycles may reach 150°F or higher. This is in the range that can potentially deactivate mold.

Heat May Not Penetrate Deeply Enough

The issue is that dryer heat primarily warms the surface rather than penetrating deep inside materials where mold growth often occurs. This limits its effectiveness on mold within fabrics, stuffing, padding or foam.

Spores and Toxins Remain

Even if the dryer stops active mold, the spores and mycotoxins still remain behind in the material or on its surface. These mold particles can lead to allergic reactions or future mold recurrence.

Repeat Drying is Often Needed

For these reasons, running an item through the dryer once is rarely sufficient. Several back-to-back hot cycles are typically required to see an effect, and mold may still return later under the right conditions.

It Spreads Mold Risk

Finally, the hot turbulent air inside a dryer can disperse mold spores to other laundry items or into the dryer itself. This can spread mold to otherwise unaffected textiles or the dryer ventilation system.

So while the dryer can provide some temporary suppression of mold, it is far from a complete or lasting solution on its own. Proper mold killing requires moisture control, thorough cleaning, sanitizing, and sometimes material disposal.

Using Heat Effectively By Material

Not all materials respond the same when subjected to heat treatment. Here is a look at how effective heat can be against mold growth on key surfaces:

Porous Materials: Low Effectiveness

Mold easily grows deep inside porous substances like wood, drywall, carpeting, fabrics, etc. Heat does not penetrate these materials well enough to deactivate the root mold structures throughout. Trying to heat these surfaces can also risk damage.

Semi-Porous Surfaces: Mixed Results

Materials like concrete, grout, or leather have some porous elements but are denser and more rigid. Heat may have a moderate effect on killing surface mold but is unlikely to impact deeper growth.

Non-Porous Surfaces: Highly Effective

Hard non-porous items like glass, metals, plastics, or glazed ceramics have the best heat conductivity. Hot temperatures can permeate to deactivate mold on both the surface and below, though the required heat level varies by material composition.

Electronics: Use Caution

Heating electronic devices like phones in ovens or dryers risks damage. Some recommend using desiccants or UV light instead to kill mold on devices while avoiding moisture or excessive heat.

As you can see, heat effectiveness correlates strongly with the density and porosity of the material infected. However, heat alone still falls short of full mold remediation even on non-porous surfaces.

Heat Treatment Guidelines and Precautions

While heat can be useful supplemental tool as part of a mold removal process, caution should be used to avoid risks:

  • Consider surface material tolerance to avoid damage from excessive heat.
  • Allow proper ventilation and air circulation during heating to prevent concentration of spores or VOCs.
  • Isolate and properly dispose of any materials that remain moldy after heat treatment.
  • Be aware of fire, burn, and inhalation dangers based on heat source. Oven heat may work better than open flames.
  • Turn off HVAC system airflow to avoid spreading spores during treatment.
  • Follow up heat with thorough HEPA vacuuming, cleaning, and drying of the area.
  • Monitor area for any mold recurrence and address base moisture issue.

While heat can provide temporary suppression of mold, always follow up with steps to remove mold residues, inhibit further growth, and tackle the underlying moisture problem contributing to the mold in the first place.

When to Call in the Professionals for Mold Remediation

For minor isolated mold growth on non-porous surfaces, DIY heat treatment may be sufficient when followed up with proper moisture control and mold prevention measures. However, if dealing with any of the following situations, it’s best to call in a professional mold remediation company:

  • Large areas of visible mold growth.
  • Signs of mold within walls, HVAC systems, carpets, or other porous materials.
  • Evidence of black mold or other toxic species.
  • Pre-existing respiratory issues or mold allergies.
  • Lack of improvement or mold recurrence after DIY removal attempts.
  • Unsure of the full scope or root cause of the mold issue.

Mold professionals have specialized tools, protective gear, and antimicrobial products to fully sanitize affected areas, repair water damage, and implement preventative measures. They can also assess if there are any hidden mold issues in building crevices or materials.

Don’t risk further contamination or health impacts of mold. Get an expert mold inspection and remediation plan.

Heat Suppression vs Total Mold Kills – What’s the Difference?

High temperatures can temporarily halt mold growth by damaging proteins and cell structures. However, heat alone will rarely kill every last mold spore or root thread buried deep in porous materials.

Mold growth may restart once conditions become mold-friendly again after heat treatment. That’s why it’s critical to follow up heat with complete mold removal and prevent future growth by fixing moisture problems.

Putting Some Heat on Mold: A Comparison of Methods

Here’s how common DIY heat techniques stack up for mold suppression and removal:

MethodTemperatureBest UsesLimitations
Clothes Dryer130-150°FNon-washable items like shoes, small toys.Doesn’t penetrate deep materials. Spreads spores in lint.
OvenUp to 500°FSmall objects like phone cases, tools, cookware.Fire and burn risks. Breathing vapors if moldy food heated.
Hot Box120-160°FBuilding materials, drywall, wood studs.Slow penetration of heat. Surface mold only.
Heat GunUp to 750°FSurfaces like tile, concrete, metals.Risk of damage to many materials.
Sauna140-190°FTreat contained rooms or spaces.Limited depth of heat penetration.

Getting the Heat Right: Tips for Max Effectiveness

  • Gradually increase temperature to allow heat to soak in rather than shocking materials.
  • Use thermometers and humidity gauges to tailor treatment and avoid under/over heating.
  • Allow proper ventilation during heating to avoid trapping moisture and mold particles.
  • Repeat shorter heat cycles rather than one long bake to allow heat to penetrate deeper over time.
  • Dispose of any materials that remain moldy after multiple heating sessions.

Conclusion: Limitations of Heat for Mold Removal

While the internet is rife with home remedies for DIY mold killing using heat, the reality is that heat alone has some clear limitations:

  • Heat primarily suppresses mold growth rather than killing mold entirely.
  • It does not remove mold spores or mycotoxins.
  • Heat is often ineffective at penetrating porous materials enough to address deep mold growth.
  • Relying solely on heat risks mold recurrence once optimal growing conditions return.

That said, heat can still play a beneficial role as part of a comprehensive mold removal process involving moisture reduction, thorough cleaning, antimicrobial treatment, disposal of unsalvageable materials, and sealing up entry points.

Whenever dealing with a stubborn mold problem, have professionals inspect, identify moisture issues, and establish a full mold remediation plan. Completely eliminating mold requires fixing the root problem, not just surface treatment.

With the right understanding and precautions, heat can be a useful addition but not an outright solution for treating mold growth in your home when discovered promptly. Stop mold in its tracks early before it becomes an invasive and complex issue.

FAQs: Your Top Heat Treatment Questions Answered

Q: Does heat kill mold permanently?

A: High heat can deactivate mold but doesn’t reliably kill all mold, especially deep inside porous materials. Spores can revive later if moisture returns.

Q: Is heat or cold better for killing mold?

A: Heat is generally more effective as extreme cold doesn’t penetrate surfaces as well. Mild cold around 40°F just slows mold growth rather than killing it.

Q: Can I use a heat gun to remove mold?

A: Heat guns work well on non-flammable bare surfaces like metal or tile but risk damaging many materials. Follow safety precautions against burns.

Q: Will putting moldy clothes in the dryer kill the mold?

A: Dryer heat may temporarily suppress mold on fabrics but does not provide deep material penetration or lasting mold removal.

Q: Can you use a sauna to kill mold?

A: Sauna heat can potentially deactivate surface mold on contained room surfaces. However, moisture contributes to regrowth if the underlying problem isn’t fixed.

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