As trained professionals in the mold industry, we often get clients who want to know if they can live in a mold free home. The answer to that question is “It depends on your definition of mold-free.” A home can have no significant mold growth but it will always have a background amount of mold spores.
Mold Growth vs. Mold Spores
To better understand what it means to be mold free, let’s take a look at an important distinction between mold colonies and mold spores. Mold colonies are comprised of branched growth structures. Each unit of growth is called a hypha (plural: hyphae). More hyphae, like building blocks, are added to the tips of the growth which spreads in multiple, branched directions. All of the hyphae combined is called the mycelium. This mycelium is what we informally call a colony. A colony of mold can usually be seen by the naked eye, but the spores cannot.
Let’s switch gears and talk about mold spores. Mold spores come from a special fruiting structure that is different from the other hyphae. These structures are typically conidiophores, from which conidia will be released. Conidia are the more scientific and accurate word for mold spore. Spores can be released via passive means such as wind movement or vibrations. Mold spores are not visible to the naked eye, unlike mold colonies.
Knowing the difference between a mold colony and a mold spore helps better understand the answer to the original question. Your home can be free of significant mold growth such as visible mold colonies growing on different surfaces, but it would be nearly impossible to be completely free from mold spores.
Can you find mold growth in every home?
Even in a well-maintained home, there are a few areas that commonly contain a small amount of mold growth. These likely have a minimal impact on the home’s indoor air quality. A common culprit is front-loading washing machines. Front loading washing machines have increased in popularity in the past decade but we commonly hear a complaint of a musty odor around these machines. The best place to check is the rubber flaps just inside of the door. Dust and debris collect inside the flaps which mold uses as a nutrient source. This is coupled with the moisture from the machine and together, you can get mold growth and a subsequent musty odor. The best way to resolve this problem is by keeping the door open when not in use, removing lint in the flaps after each use, and periodically wiping down the rubber.
Shower grout, drain pipes, and refrigerator drip pans can also sustain a limited amount mold growth. Since water tends to be readily available in these areas, mold simply needs a nutrient source to sustain it. What could be feeding the mold is these places? You guessed it – dust and debris that gets trapped in these areas. In the case of your shower, soap scum and skin cells also play an important role.
Spores in a Clean Home
We’ve established that mold spores are everywhere but you may now be wondering what the “normal” levels of mold should be in a typical home. The word normal is in quotation marks because that term is relative. There is no government standard that gives a numeric cut off for the levels and types of mold that are considered safe or elevated.
To determine if there is an elevated amount of mold inside of a home, multiple air samples are taken including an outdoor control. The outdoor control is crucial because it gives a basis to compare the indoor samples.
Some research has been done to quantify the levels of different types of mold. For example, EMLab P&K, a commercial laboratory, maintains a database of outdoor mold spore levels based on 260,000 outdoor samples in different states. In the 50th percentile of the samples for Illinois, there are between 1,000 and 2,000 spores per cubic meter in the air outdoors, and presumably, that would be a common amount to see indoors as well 1.
So with some back of the envelope calculations, a 2,000 square foot home might have over 10 million spores inside! That is not a mold free home.
Can a home be mold free?
No, a home cannot be totally free of mold DNA. However, a home can be free of mold growth (not counting a small amount that could be found in a drain pipe, etc.).
If you have concerns that there is mold growth in your home, a company like Indoor Science can do an inspection, take air samples, and be able to tell you if there is visible mold growth or an unusually high level of mold spores in your property’s air.