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Mould Contamination Levels

How severe is the mould problem?

mould contamination

Once you have had a mould inspection to determine the severity of the mould problem, the mould inspection report will classify the problem. This will allow you to make an educated decision on the best way to tackle the problem of mould removal.

When determining the appropriate remediation level, it is important to consider both the total area affected (the perimeter of affected materials) and the density of the mould growth.

These are arbitrary thresholds and are offered as guidelines only. Again, it is recommended that a qualified remediation specialist be consulted to determine the specific requirements of the project.

The Mould Level Classifications are as follows:

“Minimal” Problem

is applied to visible or anticipated surface contamination of less than 10 square feet ft². “Minimal” Problem describes situations where visible growth is mainly limited to:

  • scattered small colonies, and
  • evidence suggests that these are only present on easily accessible non-porous surfaces.

“Moderate” Problem

is applied to: areas larger than 10 ft² of surface contamination but less than 100 ft²; or on very heavy and continuous growth covering less than 10 ft².

  • light and spotty visible growth on porous or semi-porous materials, or
  • when about half the area is covered by mould colonies on non-porous materials, or
  • when other evidence (for example, a short-term moisture problem or some mould odours) has been identified and suggests that additional hidden contamination is present.

“Major” Problem

is applied to: visibly mould-contaminated surfaces that are larger in area than 100 ft, or very heavy and continuous growth covering less than 100 ft².

For “Major” problems, the possibility of extensive hidden contamination has been explored, and has been found to be a factor in determining the level of contamination.

  • a heavy distribution (covering half the area) of many large colonies on any type of material, or
  • when evidence suggests that hidden contamination is present and may be well established (for example, knowledge of a long-term moisture problem and strong persistent mould odours).

These contamination levels correspond to Remediation Protocols for Removal Procedures and Safety.

Mould Levels – Inspection Findings Required Remediation Level Safety Equipment
Minimal Problem Level l N95 face mask, gloves, eye protection
Moderate Problem Level ll Half face mask or better, gloves, coveralls, eye protection, negative air
Major Problem Level lll Full face Mask or Respirator, Full remediation suit, negative air and clean room