Life Cycle of Mold

study of mushrooms

May 1, 2020

Originally Published: 1/26/2016.

In this post, we will walk through the ways in which mold develops. The where’s, the how’s, and the why’s…which will hopefully provide you with some useful information for tackling those suspicious spots on the ceiling, or that strange odor in the air ducts. For an introduction to mold, click here.

So, you want to learn more about the development of mold?

First and foremost, mold can only develop when the environment is just right: moisture must be present, there must be an ideal temperature, and there must be some kind of food source. Under these conditions, mold will appear, then appear some more, and continue to reproduce via its life cycle. This life cycle occurs in four stages:

#1. Hyphae Growth: Hyphae are thread-like filamentous cells that release enzymes used for both degrading and absorbing nutrients from a substrate (i.e. organic debris, cellulose, wood, almost any carbon containing material including human skin—the food source). Once it has gotten its fill, so to speak, the hypha will grow into a mycelium, which is the main body of the fungus… or, for the non-mycologists: the part that you can see.

#2. Spore Formation: The formation of spores is dependent on a variety of environmental factors including light, oxygen levels, temperature, and nutrient availability. When the conditions are right, spores will form on the ends of some hyphae cells.

# 3. Spore Dispersal: After the spores form, they are released into the air and carried elsewhere to begin the process of germination, and begin the cycle anew. Mold spores are highly resistant and durable; they can survive in a dormant state for years in both hot and dry environments.

#4. Spore Germination: Once the spore has settled in its new home, and had plenty of water and food, then it will begin to germinate and develop into a new hyphae cell.

An illustration of this process is shown below.



Because of the high humidity and high temperatures, Houston provides mold a very inviting environment, especially in those spaces found inside the HVAC ventilation systems in houses and office buildings.

The inside of the air handler units are built to contain some moisture-specifically, the condensation created by the cooling coils, which is then collected in the condensate pans; these anticipated moisture levels can rapidly get out of hand with Houston’s humidity. If the HVAC system is not cycling properly (because the cooling coils are dirty, or because the registers in parts of the house are not open), then the air handler unit won’t be able to remove humidity from the air, which thereby allows the extra Houston moisture to travel down the air distribution system.

Systems that are not running properly will cause an increase in humidity level for an entire facility, which includes inside the air handler unit, and throughout the ductwork.

But wait…there’s more!

Mold gets nutrients from many sources:

  • Construction dust in brand new systems
  • Dirt and debris entering the system from cheap filters, improperly sized filters, dirty filters
  • Dirt and debris entering the system from leaks in the system that completely bypass the filters.

Regardless of how the dirt and debris enter, once it’s there, you’re in trouble. Dirty internally lined air handlers, plenums, risers, and ductwork will provide an ideal environment for the life cycle of mold.

Avoiding these conditions is the best measure to prevent mold inside the HVAC system. However, if it does occur, then proper remediation is recommended to provide the best indoor air quality.

If you are concerned about the state of your HVAC system, then give us a call today so that we can give you a free estimate for HVAC system cleaning!

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