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The Basics

Moulds are microscopic fungi that can be found almost anywhere, both indoors and outdoors. Mould can grow anywhere that satisfies four primary conditions:

  1. Presence of mould spores – spores are everywhere, and it is very difficult if not impossible to remove them completely.
  2. Appropriate growth surface or nutrient source – moulds are adaptable and can grow on almost any surface; many moulds especially like cellulose-based materials (e.g., wood, drywall, insulation, cardboard, paper, carpet, etc.).
  3. Appropriate temperature – although many moulds grow best in warmer temperatures, given enough time, mould can grow at almost any temperature condition.
  4. Water – this is the most significant and most important criteria since the other conditions are too commonly available to be controlled. The consensus of most organizations with a perspective on air quality (e.g., WHO, EPA, AIHA, ASHRAE, etc.) is that controlling moisture and dampness is the only way to consistently control or limit mould growth.

Mouldy Odors

Microbial volatile organic compounds (MVOCs), are substances naturally produced by moulds as they grow and digest the surface they are attached to. MVOCs often have strong or unpleasant odours and they can be the source of the “mouldy odor” or musty smell frequently associated with mould growth.

Mould has a damp, musty smell —similar to what you’d smell after opening an old book. “In general, smell is not a good way to determine if there is a mould problem,” says Laureen Burton, a staff chemist and toxicologist for the Environmental Protection Agency (EPA). The smell of indoor moulds can differ depending on the type of mould, the surface on which it’s growing, and its source of moisture. Plus, she says, some people don’t notice a smell at all.

A mouldy or musty odour should be investigated. When you have mould growing hidden away in your house, often a mouldy smell might be the only clue that it’s there. Don’t ignore mould odours just because  you can’t see any mould. You should thoroughly inspect your home before any moisture issues become worse.

Mould can grow undetected in many places:
  • inside walls, like in the picture above
  • in attics
  • under carpet
  • under vinyl or linoleum flooring
  • under floorboards
  • above ceilings
  • under wallpaper
  • in the insulation in your walls
  • in your home’s heating, ventilation and air conditioning system
There are no government  standards (OSHA, NIOSH, EPA) that have been established for mould in residential or commercial buildings, so it is impossible to prove that a building or room complies with any health regulations concerning mould exposure.

MoldScan™ detects actively growing mould by measuring the levels of  microbial VOCs (MVOCs) produced by active mould growth. We are the only laboratory that has been successful in developing this type of technology which measures mould metabolites down to  the parts-per-trillion (ppt) level.

What are Mycotoxins?

Mycotoxins are toxic compounds that are naturally produced by certain types of moulds (fungi).  More than 200 mycotoxins have been identified from common moulds, and many more remain to be identified. Only a small number are associated with indoor moulds and pose any human health risk. Some of these moulds are commonly found in moisture-damaged buildings. The amount and types of mycotoxins produced by a mould depends on many environmental and genetic factors. No one can tell whether a mould is producing mycotoxins just by looking at it.

Mycotoxins are considered to be semi-volatile compounds. These toxins released by mould do not remain in a gaseous state for long though a small amount may linger. Being  semi-volatile, the compounds are bigger and heavier therefore requiring a  higher temperature to move from a solid state to a gaseous state (~200°C). After being released from the mould these toxins quickly condense and attach to other particles in the air and settle on surfaces. For this reason, mycotoxin exposure is typically through skin contact and ingestion of these fine particulates in the home.

Our test does not analyze for Mycotoxins.

Health Effects

Symptoms of exposure to mould and MVOCs:
  • headaches
  • nasal irritation
  • dizziness
  • fatigue
  • nausea
  • coughing
  • sneezing
  • sore, itchy throat
  • congestion and runny nose
  • sinus headaches
  • wheezing and difficulty breathing
  • itchy, watery eyes
  • irritated, itchy skin

Sensitive individuals should avoid areas that are likely to have mould, such as compost heaps , cut grass, and wooded areas. Inside homes, mould growth can be slowed by controlling humidity levels and ventilating showers and cooking areas. If there is mould growth in your home, do not delay remediation.

How can you decrease your mould exposure?

Mould particles are found everywhere; controlling moisture is the key to preventing mould growth. Sources within homes, businesses, and schools include leaks through roofs, walls, and basements; condensation on windows and in bathrooms; standing water in drains, on floors, and in heating, cooling, and dehumidifying equipment; heating/cooling ducts; and wet floors and carpets.

Preventing mould growth requires preventing leaks, removing standing water, venting areas prone to condensation (especially bathrooms and kitchens), and immediately drying or removing damp carpets and furniture. Mould-inhibiting paints can be used indoors, and air conditioners and dehumidifiers can be used in humid weather.

It is possible to assess a  building for mould, beyond a visual inspection, if mould is suspected. However, there is little consensus as to the standards for mould inspectors, testing methods, normal amounts of mould, or reporting formats. This makes it difficult to interpret test results and their potential implications.

Effective personal protective equipment (PPE) is critical when considering removal of mould . Large amounts of mould may require specialized containment and removal techniques. The U.S. Environmental Protection Agency described the necessary steps in a document entitled “Mold Remediation in Schools and Commercial Buildings”. However, this document is applicable to mould removal in homes as well.

In the UK, BSI PAS 64 is a code of practice for the mitigation and recovery of water damaged buildings. PA 64 includes industry standard guidance on the removal of contamination, including mould.

If mould is clearly present, as determined by visual inspection or a reputable inspector, removal is paramount as it can destroy the materials it grows on and is associated with human health problems. Small amounts of mould on hard surfaces can be removed with commercially available mould and mildew removers. Follow product instructions carefully to avoid breathing fumes, skin contact, or splashing chemicals in the eyes.

You can’t always see the mould

Mould particles are very tiny, microscopic, in fact. They are also very lightweight and easily drift in the air from place to place.

Things to look for:


Anywhere you have moisture in your home you have the potential for mould.



Any type of discoloration on a wall, ceiling, or floor.


Ventilation problems

Homes that are tightly sealed  can lead to condensation  issues that promote mould growth.

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