Indoor Air Quality (IAQ) is one of the most complex challenges facing the building industry today. Of all potential IAQ concerns, mould (mold) and moisture combined are by far the most serious of the IAQ challenges facing the building management and construction industry today. In fact Volume 2 of the Barrett Report (on leaky condos) determined that mould (mold) and moisture resulting from building envelope failures can impact both the structural durability of the building and the health of both the building occupants and the construction workers.
Our firm, Sterling IAQ Consultants Ltd. has become directly involved in this issue investigating concerns resulting from exposure to mould (mold) in moisture troubled buildings.
A recent International Conference, Healthy Building 2000, identified mould and moisture in buildings as a worldwide problem. Microbial contamination of building envelopes and mechanical systems was identified as the single most important IAQ issue of international attention.
Growth in Buildings
Mould (mold) and moisture damage to the building is caused by a number of factors:
- Moisture and condensation in the HVAC System.
- Leaks in the building envelope from the foundation up to the roof.
- Leaks caused by faulty plumbing or poor workmanship.
- Moisture existing in the building materials before construction and sealed into the envelope.
- Moisture caused by occupant activities such as showering or bathing.
- Moisture caused by combustion sources particularly open flame cooking and heating appliances such as stoves and water heaters.
- Poor site drainage.
Principles of Mould Assessment
Based on this protocol, Sterling IAQ Consultants Ltd. conducts inspections of HVAC systems and buildings for signs of moisture and/or visible mould growth. Sometimes baseboards and carpet are pulled back and other times a boroscope is used to inspect wall cavities or inside ductwork.
Based on the results of our visual inspections, there may be a need for sampling. There are three basic sampling methods used to assess mould contamination in buildings:
- Bulk sampling
- Surface sampling
- Air sampling
Bulk sampling involves aseptically cutting a sample of material such as wallboard, insulation, settled dust, or carpet; and determining contamination of viable organisms. This method produces qualitative rather then quantitative results by detecting the presence of a mould on or in the sample.
Surface sampling involves aseptically collecting a sample from the surface of a material such as shelves, walls or pillars. There are various methods used to collect the sample including: wetted swab, tape lift, contact plate, or a suction device such as a micro vacuum.
Again this method produces qualitative rather than quantitative results identifying the presence of a mould.
Air sampling is a method used to sample air in the occupied space of a room, in the building envelope or in the ventilation air provided by the HVAC system serving a building to determine biological contamination. There are two commonly used sampling methods:
- Total (viable + nonviable) spores – generally called spore trap sampling and has become the primary method for air sampling
- Viable (culturable) spores – was once the gold standard of testing but has decreased in popularity