Mold and Mildew

Mold is a microorganism that has tiny seeds, or spores, that spread through the air and feed on organic matter wherever they land. It has been in existence throughout human history, and actually contributes to the life process. There is literally mold in every breath we take.


There are thousands of known species of molds, many molds such as mildew that commonly appear on ceramic tiles in bathrooms and window frames are considered benign and do not usually constitute a health threat, but they should be removed.


Some are characterized as allergens and are relatively benign but can provoke allergic reactions among sensitive people.


Others characterized as pathogens can have adverse health effects on large segments of the population, such as the very young, the elderly, and people with suppressed immune systems.


The most dangerous and less common molds are called toxigens and represent a serious health threat.

All molds flourish in the presence of moisture and in a home the sources of moisture include roof leaks, plumbing leaks and condensation.

The areas of a home where condensation can collect are:

  • Bathrooms and kitchens
  • Metal window frames and single pane windows
  • Areas in a rooms walls or ceilings where insulation is missing
  • Attics
  • Crawlspaces and basements
  • Improperly installed vapor barriers
  • Unheated interior rooms
  • Ducting for furnaces, heat exchangers, air conditioners etc.
  • Vent pipes for dryers, kitchen and bathroom exhaust vents

Keeping a home well maintained, heated and properly ventilated is the best defense against giving any type of mold an opportunity to establish itself.

CMHC Fighting Mold

If you suspect mold in your home and are concerned or would like to know how to clean it please visit CMHC’s Homeowners Guide (Fighting Mold)

Although some mold-like substances may be visually identified, the specific identification of molds can only be determined by specialists and laboratory analysis.

  • Stachybotrys chartarum – Mildew

Other molds that have been used in food production include:

  • Fusarium venenatum – quorn
  • Geotrichum candidum – cheese
  • Neurospora sitophila – oncom
  • Penicillium spp. – cheese
  • Rhizomucor miehei – rennet for making vegetarian and other cheese
  • Rhizopus oligosporus – tempeh
  • Ustilago maydis – filling in tortilla-based foods

Alexander Fleming’s famous discovery of the antibiotic penicillin involved the mold:

  • Penicillium chrysogenum.