Mold is an unwelcome guest in many households, posing significant health risks and causing structural damage. The battle to eliminate mold often involves various cleaning solutions, including ammonia. But does ammonia effectively kill mold, or are there better alternatives? In this blog of Mold Assassins, we will explore the role of ammonia in mold removal, compare it to other cleaning solutions, and provide guidelines on when and how to use it safely.

What Is Ammonia?

Ammonium hydroxide dissolved in water is a common ingredient in household cleaning products. Known for its strong cleaning properties, ammonia is particularly effective on non-porous surfaces like glass and stainless steel.

The Role Of Ammonia In Mold Removal

ammonia in mold removal

The primary question is: Does ammonia kill mold? The answer is yes but with limitations. Ammonia can kill mold on non-porous surfaces by breaking down the mold’s structure. However, its efficacy is limited to surface mold. On porous surfaces such as wood, drywall, and fabric, ammonia cannot penetrate deeply enough to kill mold at its roots. It might only prevent mold from returning if underlying moisture issues are addressed.

Porous vs. Non-Porous Surfaces

Knowing the difference between porous and non-porous surfaces is crucial in mold remediation:

  • Non-Porous Surfaces: These surfaces do not allow air or liquid to pass through, making them easier to clean. Examples include glass, metal, countertops, sinks, bathtubs, and tiles. Ammonia is effective on these surfaces as it can directly contact and kill mold.
  • Porous Surfaces: These materials, such as ceiling tiles, carpets, insulation, and wood, absorb and trap mold spores deep within. Ammonia is ineffective on these surfaces because it cannot reach the mold growing inside.

Ammonia should be diluted properly to clean mold on non-porous surfaces. A mixture of equal water and ammonia in a spray bottle is typically effective. Apply the solution, let it sit for 10-15 minutes, scrub the area, and then rinse thoroughly with water. Ensure the space has good airflow, and wear gloves and a mask to protect yourself from breathing in strong smells.

How Does Ammonia Effectively Kill Mold?

Ammonia can be an effective solution for killing mold, but its efficacy depends on factors such as the type of mold and the surface it has contaminated. Ammonia works well on non-porous surfaces like glass and tiles but is less effective on porous surfaces like wood or drywall.

To use ammonia to remove mold, follow these steps:

  1. Prepare an Ammonia Solution: Mix equal parts of household ammonia and pure water in a spray bottle. This diluted solution is safer and easier to handle than undiluted ammonia.
  2. Spray and Wait: Apply the ammonia solution to the mold-affected area using the spray bottle. Ensure the area is well-saturated, and let the solution sit for at least five minutes to penetrate the mold.
  3. Scrub Gently: After the solution has sat, gently scrub the mold-infested area with a brush or sponge to help dislodge the mold.
  4. Rinse and Repeat: Rinse the area with clean water and dry it. If mold remains, repeat the process until it is completely removed.

Alternative Of Ammonia To Kill Mold?

mold removal

If ammonia’s mold-killing capabilities are limited, what other options are available? Let’s compare ammonia with other household products known for their mold-cleaning properties: bleach, hydrogen peroxide, and white vinegar.

  • Bleach: Often the first choice for mold removal, bleach (sodium hypochlorite) effectively kills surface mold on non-porous materials. However, like ammonia, bleach cannot penetrate porous surfaces. It is also essential to avoid mixing bleach with ammonia, which produces toxic fumes.
  • Hydrogen Peroxide: More versatile than bleach and ammonia, hydrogen peroxide can kill mold on porous and non-porous surfaces. Hydrogen is less likely to produce harmful fumes but can bleach fabrics and other materials.
  • Baking Soda: Baking soda is another non-toxic and effective mold cleaner. Soda works well on both porous and non-porous surfaces. Baking soda not only kills mold but also absorbs moisture, which helps prevent future mold growth. It can be used alone or combined with vinegar for enhanced effectiveness.
  • White Vinegar: A non-toxic alternative, vinegar kills about 82% of mold species. It is less potent than bleach and hydrogen peroxide but is safer and more eco-friendly. Multiple applications and more effort may be required for effective mold removal.

When Should You Use Ammonia To Kill Mold?

Ammonia is most effective for small-scale mold problems, particularly on non-porous surfaces. Here are some scenarios where ammonia can be a suitable choice:

  • Bathroom and Kitchen Mold: Ammonia can effectively tackle mold in bathrooms and kitchens with high moisture levels.
  • Glass and Tile Surfaces: It works well on glass shower doors, tiles, and other non-porous surfaces where mold growth is visible.
  • Mild Mold Infestations: Ammonia can be a practical solution to a small and manageable mold problem.

The Downsides Of Using Ammonia

While ammonia can be an effective mold-killing agent, it is important to understand the associated risks and take appropriate precautions when removing mold.

  • Harsh and Toxic Nature: Ammonia is considered hazardous when used improperly. It can release harsh and toxic fumes when inhaled. Remember to keep good airflow by opening windows and doors, using fans, and wearing a mask if needed. Always wear protective gear, such as gloves and goggles, to shield yourself from contact with ammonia solutions and their fumes.
  • Never Mix Ammonia with Chlorine: Mixing ammonia and chlorine-based products creates harmful and potentially deadly gases. Always use these products separately and follow the manufacturer’s instructions.


Ammonia can be a useful tool in the fight against mold, particularly on non-porous surfaces. However, its limitations on porous materials and potential health risks mean it should be used cautiously. Professional remediation is recommended for severe mold problems, especially those involving porous surfaces, to ensure complete removal and prevention of future growth.

By understanding the strengths and limitations of ammonia and other cleaning solutions, homeowners can make informed decisions about mold remediation and ensure a cleaner, safer living environment.