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November 17, 2005

Ask Darrell - Issue 46

Toxic black mould - Part 1

Darrell Paul

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Often we hear stories or news reports of homes being condemned due to mould contamination. You see TV programs that scare the pants off you that speak of the ordeal some family has had to endure in dealing with mould.

Just search mould on the internet. You will find countless sights and companies more than willing to scare you into believing that mould is the end of our planet as we know it.

What is the truth? Well, truth is, there is very little factual information, and a lot of hype and hysteria.

Here’s what we do know for sure. Our planet is made up of all kinds of fungi. If you enjoy a beer or glass of wine with your supper, perhaps some blue cheese dressing or soy sauce, you are enjoying a type of mould.

If you get sick due to bacteria, you will most likely get a penicillin or other mould derived prescription.

In fact over 25 per cent of life on our planet is from the fungi or mould family. Just imagine what your yard would look like in the spring without these little cleaners.

Having said that, there is still a reason to be careful and not allow mould to grow in your home. How can this be accomplished.

First, you need to understand what causes the mould to grow in the first place. Mould is how the earth cleans itself. There are four requirements for mould growth.
• Moisture
• Heat
• Food source
• Mould spores

Moisture must be very high over an extended period of time for most wood products. This is not necessarily true for paper similar materials.

An average of 70 per cent relative humidity or 20 per cent moisture content is required. If you get water in your walls, roof, basement, you need to dry it immediately. Mould can begin in as little as 24-48 hours.

Heat is also required. Not a lot but at least room temperature. Mould prefers warmer locations and usually about 18 to 35 degrees Celsius is its preference.

Food sources are anything cellulose in nature. Drywall paper, sawdust, OSB, and wood. Actually, wood is pretty resistant in its solid form. The resins and formaldehyde in OSB make it more susceptible.

Something that would be considered durable is when the food source is removed, such as treated lumber.

Finally, to produce mould you require the spores, which are like seeds. These are everywhere. You can’t go anywhere without mould spores.

Incidentally, these are the things that cause all the grief for us in the first place. Spores are released by mould that is dying, such as when it dries. Its how it keeps itself from being completely killed off.

In our population most of us are unaffected, however there is a small percentage that are adversely affected by these spores. Individuals with allergies or asthma, as well as young children can all be affected.

When you think about it, for the most part we are pretty safe. It is like taking a prescription of penicillin. Most of us are helped and unaffected, however what about those who are allergic?

Every time I hear or read about some catastrophic mould problem and I get the details, its usually not something common place. Mostly it is a result of years of neglect.

Next time I’ll discuss what to do if you suspect mould is an issue in your home.  NHS



Darrell Paul, Building Consultant, has dedicated his entire career to the residential building industry. He is president of Building Science Resources, is a director with the Professional Home Builders Institute of Alberta (PHBIA) and is an accomplished speaker/presenter in addition to instructing home building and building science courses with SAIT.

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