Health Information and Tools > Health A-Z >  Mouldy Homes and Buildings: Managing Indoor Mould
Facebook Tweet Email Share

Main Content

Environmental Health

Mouldy Homes and Buildings: Managing Indoor Mould

​​​​What if I find mould in my home or building?

  • You have to find what’s causing the moisture problem and correct it or the mould will com​e back. You may need the help of a building expert (e.g., construction engineer, building repair, or construction specialist) for foundation, roof, or exterior wall problems. You may need a plumber for leaky plumbing fixtures or sewer back-ups.
  • Find and remove any mould and material contaminated by the mould. It’s important to protect yourself and other workers while you’re doing this.

Tips to Clean and Remove Mould (Mould Remediation)

Porous and Semi-Porous Material

Porous material has openings on the surface or has cavities inside.

  • Because they can’t be cleaned well enough, remove mouldy porous materials (e.g., carpet, upholstered furniture, wall-board, ceiling tiles, clothing, books, and pressed wood products). Some porous materials may be restored by restoration specialists.
  • Replace porous materials such as filters and insulation lining ducts if there is mould growing in an HVAC system. You will likely need to call a company that deals with HVAC systems.
  • With semi-porous material like wood framing, the surface often can be cleaned and the material left in place. If the mould has penetrated into the material, the material must be removed.

Non-Porous Material

  • Non-porous material such as metal, plastic and glass usually can be cleaned.
  • Clean non-porous materials by methods like HEPA-vacuuming, wiping with a damp cloth, pressure washing, etc.


  • Using a biocide (like chlorine bleach) isn’t usually recommended. Biocides may be needed because of sewer back-ups or surface flood waters.
  • HVAC manufacturers may recommend using biocides on certain HVAC parts. Check with the manufacturer for the products they recommend for use in their systems. Biocides that can be used in duct systems are very limited. They must not leave any residue in the HVAC system and must be certified by Health Canada.

Protecting Yourself

Most important is protect yourself or other people.

  • Make sure no one is in the work area other than the people doing the cleaning.
  • Try not to disturb the mouldy surface/material to decrease the spread of mould spores through the area. You can help prevent spreading the spores through the air by first misting (not soaking) the area with water.
  • Put all waste with mould on it into a plastic bag and seal it. You can throw the bag away in a regular outdoor garbage bin.
  • For all cleaning work, scrub surfaces with cleaning agents (e.g., soap and water solutions).
  • Clean the work area and exit pathway well (e.g., HEPA-vacuum or wipe with a damp cloth) once the remediation is finished.
  • Leave all work areas dry and visibly free of contamination and debris.

Depending on the type of building, the size of the remediation, or how long it takes, professionals other than the building owner may need to be involved:

  1. Less than 1 square foot of mould contamination that is close together (contiguous)
    • These areas can be easily cleaned by building owners or regular maintenance staff using standard cleaning techniques: scrubbing surfaces clean using a cleaning agent (e.g., soap and water solutions). Using personal protective equipment (PPE) is up to you but is recommended. At the very least, wash your hands as soon as you are done the work.
  2. Between 1 and 10 square feet of mould contamination that is close together (contiguous)
    • These areas can be easily cleaned by building owners or regular maintenance staff using standard cleaning techniques: scrubbing surfaces clean using a cleaning agent (e.g., soap and water solutions). People doing the remediation should be trained on clean-up methods, personal protection, and know of the possible health hazards. At the very least, personal protective equipment (PPE) should include a disposal N95 respirator and disposable gloves.
    • It’s recommended that infants less than 12 months old, people with weakened immune systems, those with a chronic lung condition, or people with allergies stay out of the area. Seal door openings, ventilation system openings (e.g., vents and grills) and other openings that let air move.
  3. Between 11 and 99 square feet of mould contamination that is close together (contiguous)

    Owner-occupied homes: it is best to hire a remediation contractor and environmental consultant. If the owner decides to do the remediation using in-house maintenance staff, the containment measures below are recommended:

    • PPE: Wear a full-face N95 respirator and disposable gloves.
    • Limited Containment: Isolate the work area with floor to ceiling plastic sheet​s with a slit entry and covering flap to contain dust/debris, and isolate unaffected ceilings, walls, or floors.
    • Isolation: Use barriers and signs to isolate and restrict access to the remediation area and prevent spreading the mould particles through the air. Seal possible routes of cross-contamination, such as the HVAC system vents and grills, pipe chases, electrical outlets, and others openings or pathways that let air move.
    • Pressurization Control: Use negative pressure so air can move into but not out of the work area. Block supply and return air vents within the ​containment area.
    • Dust Suppression: Mist (not soak) surfaces before starting to prevent the mould spores from becoming airborne.
    • Post-Removal Cleaning: Once the work is finished, HEPA-vacuum or clean the work area and surrounding areas with a damp cloth and/or mop and a detergent solution. Make sure all exposed surfaces that are part of the building are wiped dry.

    For rental accommodations, public facilities (e.g., schools, daycares, hospitals) and commercial buildings

    • A remediation contractor and environmental consultant must be hired. The consultant is an independent third party who provides quality assurance/quality control (QA/QC) for the remediation work to both Alberta Health Services (AHS) and to the owner.
  4. For 100 square feet or more of contiguous mould contamination and Marijuana Grow Operations (MGOs):
    • A remediation contractor and expert consultant should be hired, even if the owners live in the home. The consultant is an independent third party who provides quality assurance and quality control for the remediation work to both AHS and the owner.
    • Expert consultant responsibilities include a thorough investigation, identification, and remediation of all moulds, both visible and hidden. 
    • MGOs must be thoroughly assessed for all moulds, both visible and hidden.

Please visit AHS Information for your Business and Community under the Rental Housing and Grow Ops heading for more information about acceptable remediation.

Current as of: November 3, 2016

Author: Environmental Public Health, Alberta Health Services