Do Mold Spores Ever Die? Is it Possible to Kill Them?

Published By: Debbie Luna
Last Updated:
March 19, 2021

Household molds are simple, living organisms. While other organisms like plants naturally die, fungi or molds do not. Rather, mold has two different life stages: viable and non-viable.

Mold spores are around you at all times and are highly airborne. Even if surface level mold is removed, mold spores will become dormant (non-viable) until the ideal conditions for growth are re-introduced. Depending on the species of mold, some spores can remain dormant for hundreds of years.

While mold spores are highly durable, there are ways that you can significantly improve indoor air quality (IAQ). In order to have a better understanding of how to improve IAQ, you first need to know how mold spores reproduce.

The Life Cycle of Mold

All indoor mold follows the same life cycle and will germinate once ideal conditions for growth are met.

1. Hypha Growth

Hypha are branching filaments that release digestive enzymes in order to metabolize substrate. As the hyphae continue to metabolize the substrate, they begin to form a large colony called a mycelium.

2. Spore Formation

Once the mycelium has matured, the ends of the hypha cells will develop spores. The formation of spores is dependent on environmental factors like temperature, the presence of moisture and oxygen, as well as the availability of a food source. If these parameters aren't met, mold will not grow.

3. Spore Dispersal

mold growth garden

Spores then disperse through the air until they reach a new environment that's suitable for germination. To reiterate, mold spores are hardy organisms that are capable of remaining dormant for years. During this stage it's possible for millions of spores to be released into the air.

4. Germination

Once the mold spores find themselves in an environment that's suitable for germination it will restart the life-cycle process by creating a new hypha cell.

Viable vs Non-Viable Mold Spores

Since mold spores are around us at all times, rather than looking at mold spores as being either dead or alive, they're referred to as either viable or non-viable.

A mold spore is essentially a seed. With adequate amounts of nutrients, ambient temperature, oxygen, and moisture, a seed will grow and a spore will germinate.

When mold “dries out” the mold spores become non-viable or inactive. However, it’s important to note that even in a non-viable state, mold spores can still cause allergic reactions like itchy eyes, dermal reactions, wheezing, and sore throat.

What Do Mold Spores Need to Grow?

In order for mold to grow it needs a food source to metabolize and moisture (water content). External factors like the presence of oxygen as well as the appropriate temperature have a big impact on the survive-ability of mold.

Food Source

Mold can only grow so long as there is substrate for the hyphae cells to metabolize. Outdoors, mold will digest dead plants, trees, and various other debris. Indoors, mold will digest drywall, wood, and paper.

While mold can't digest non-carbon containing materials like metal and cement, it can digest dust particles that settle on the surface of these materials. As a result, mold can also germinate and grow on them.

Moisture Content/Humidity

Mold requires water in order to grow. Climates that have high levels of relative humidity (greater than 60 percent) have more water vapor in the atmosphere. When humid air comes into contact with structures that are colder than the air, the water vapor condenses.

Surfaces like gypsum drywall, wood, flooring material and other structural surfaces are porous and will readily absorb moisture. As a result, mold will grow in and on these surfaces. This is why homeowners are recommended to enhance the quality of ventilation in their homes. We suggest you carefully study this extensive write-up on the dangers of poor ventilation.


Like humans, molds require oxygen in order to grow. Molds can also survive at low levels of oxygen.


Most indoor molds cannot grow below 40 degrees Fahrenheit. For this same reason, food is refrigerated at 39 degrees Fahrenheit.

Mold grows best at temperatures between 60 – 80 degrees Fahrenheit. This temperature range is also what most humans find comfortable to live in.

How to Control Mold Spores in the Home

While mold spores may be around you at all times, there are ways to prevent mold from being viable:

Humidity Levels

Humans are particularly sensitive to humidity levels. Sweating is an autonomous process where-in sweat travels through tiny tubes to the epidermis. The sweat then evaporates and cools the surrounding skin.

Humidity is then a measure of the amount of water vapor (gas) in the atmosphere. Meaning, a relative humidity of 100% means the air is completely saturated with water vapor and can’t evaporate anymore. This is why you feel much hotter when humidity levels are high, while the temperature may feel normal.

Elevated levels of humidity cause the same problems in the home. When warm, moisture-laden air contacts a cold surface like plumbing, walls, duct-work, etc, it results in condensation on these surfaces.

humidity moisture window

In order to combat humidity, you can:

  • Invest in a dehumidifier
  • Use exhaust fans in your bathroom and kitchen
  • Open doors and windows to ventilate the space (close them when it rains)
  • Ensure that your dryers duct-work has short runs and is exhausted outdoors

Air Purification Systems

Mold spores are the reproductive unit for fungi. By filtering the air around you, you can effectively remove mold spores and prevent the various allergic responses detailed above. Keep in mind that no matter the capacity of the air purifier, you will not be able to remove ALL mold spores from the air.

There are a number of air purifiers available, however they are mainly separated by their method of filtration. In terms of removing mold from the air, you should look for a filter that uses True HEPA or High Efficiency Particulate Air.

A HEPA filter is rated to remove 99.97% of particles as small as 0.03 microns. A typical mold spore is 4 – 30 microns in size. While HEPA filters are effective at removing mold spores from the air, they need to be changed regularly. If they aren’t, they can also become a viable surface for mold to reproduce.

Debbie (Deb) started powerlifting and Olympic lifting in High School as part of her track team's programming; She continues to train in order to remain athletic. Inspire US allows Deb to share information related to training, lifting, biomechanics, and more.
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