Mould Overview

Even though it’s been around for thousands of years, mould is a relatively new issue of concern in residential housing. Moisture from roof leaks, hidden plumbing leaks and basement water penetrations are the most obvious potential contributors to an interior mould problem.

What Is Mould?

Moulds are simple, microscopic organisms whose purpose in the ecosystem is to break down organic materials. They can be found wherever there are organic materials and moisture, which are the necessary ingredients for mould growth. Moulds are found both indoors and outdoors, and in any area of the country. Some are visible, some are not.

Except in structures where all of the incoming air is cleaned, there is never going to be a “mould-free” condition. Therefore, when checking a house for mould, the intent is to have the indoor mould condition equal to or lesser than the outdoor condition. Mould screening of the indoor and outdoor conditions determine if an outdoor mould problem exists and what types of moulds are growing indoors. Conditions Tending to Produce Mould Growth

• Moisture. When looking for the source of a mould growth look for moisture. Spores can survive in as little as 65% humidity.
• Food Source. Food sources for mould are the organic materials in a structure, such as wood, drywall, insulation, and natural fibers, which may have been exposed to moisture.
• Raw Materials. Even before a new home is built, its raw materials can collect moisture and mould. This is especially the case when exposed to the weather.
• Minimal Air Circulation. An example of minimal air circulation is two pieces of wood coming together, such as where a floor joist meets a band joist.
• HVAC Systems. HVAC systems and ductwork often contains porous materials, moisture, and dirt.

Sampling Methods for Mould and Bacteria Testing

Tape Samples

2-3 inches of clear tape are pressed gently onto the surface to be tested for mould growth.

Bulk Samples

Approximately 4 square inches of the suspect material (e.g., carpet, drywall, wallpaper, wood, etc.) while taking care not to disturb the mould.

Swab Samples

Using dry swabs for wet surfaces and wet swabs for dry surfaces, swab the test surface by rolling the swab lightly back and forth.

Air Samples (Non-Culture)

umetric air samples are taken by impacting a known volume of air into a cassette with a sampler pump.

Air Samples (Culture)

umetric air samples for culture analyses are taken by impacting a known volume of air onto a suitable growth medium.