Categorized | Just Cause

INDOOR AIR QUALITY – What Does the Law Require You to Do to Protect Workers from Mould?

Not too long ago, reports on the dangers of “toxic mould” were all over the news. The moulds that allegedly pose the most danger are ones that contain mycotoxins. Although the verdict is still out on exactly how dangerous exposure to mould and mycotoxins is, scientists agree that exposure to mould may cause certain ailments, such as eye or nose irritation, asthma, headaches, fatigue, sore throats and skin rashes. Those who are particularly vulnerable include the very young and very old, and individuals who have allergies, respiratory problems, pulmonary disorders or compromised immune systems.

Why should an EHS coordinator care about mould? Naturally, you don’t want any of your workers to get sick because of exposure to mould at your workplace. But there’s another, more immediate reason to protect your workers from exposure to mould: The laws require you to do so. Where does this legal obligation come from? And what does it require you to do? This article will answer those questions.

We’ll explain how the different provinces and territories protect workers from exposure to mould and outline the measures that employers are required to take. We’ll also give you a chart on page X spelling out what each province and territory has to say about mould in the workplace.


Where in the law does it say that employers have to protect their workers from exposure to mould? Answer: Nowhere. None of OHS laws in the provinces and territories specifically address mould. But that doesn’t mean you’re not required to protect workers from exposure to mould in the workplace. Confused? Don’t be. Keep in mind that the duty to protect workers from a particular hazard not mentioned in the law can be implied from other, more general obligations under the law. In the case of mould, the implied obligation comes from three sources:

1. Indoor Air Quality Requirements

Even though they don’t mention mould, the OHS regulations of most provinces and territories require employers to control the quality of the air in the workplace through means such as proper ventilation or have specific requirements for dealing with air contaminants. These indoor air quality requirements could be read as applying to mould.

For example, in NB, employers must ensure that workers’ exposure to air contaminants doesn’t exceed threshold limits. The definition of “air contaminant” includes “any gas, fume, smoke, vapour, dust or other airborne concentration of a substance that may be hazardous to the health or safety of a person” [OHS General Reg., Secs. 2 and 24(1)]. Mould could easily be considered to be one of the “other airborne substances” subject to exposure controls. And in NS, employers must keep workplace air reasonably pure and “render harmless all gases, vapours, dust or other impurities that are likely to endanger the health or safety of any person” [OHS General Reg., Sec 15]. And mould could be considered an “impurity.”

BC’s regulations require employers to investigate indoor air quality complaints and to take samples of airborne contaminants [OHS Regs., Secs. 4.79(1) and (2)]. And the province has issued guidelines that specifically say that the indoor air requirements do apply to mould. But the Insider isn’t aware of any other province or territory that has done likewise. Nor could we find a court case that made such a ruling. So we can’t be 100% sure that provinces and territories outside of BC would interpret their indoor air requirements to require employers to protect workers from mould. On the other hand, it’s reasonable to believe that regulators and courts in other parts of Canada could follow BC’s lead and find employers who failed to protect their workers from exposure to mould liable for violating indoor air quality regulations.

2. Biological Hazards Requirements

OHS regulations typically require employers to protect workers from biological hazards or from biological substances that could pose a health or safety risk to workers. And that requirement could apply to mould.

For example, in AB, employers must take steps to minimize workers’ exposure to “harmful substances.” The OHS regulations define “harmful substances” as substances, including biological hazards, that create or could create a danger to the health and safety of workers exposed to them [OHS Regs., Secs. 1(k) and 15(3)]. This language covers mould. How do we know? The AB government issued a biological hazard bulletin on workplace mould saying that the OHS Act requires employers to protect the health and safety of workers and when exposure to harmful substances—such as toxic moulds—are identified, employers must establish procedures to minimize worker exposure.

3. General Duty Clause

In most provinces, the duty to protect workers from exposure to mould comes from what’s commonly known as the “General Duty” clause—that is, the part of every province’s and territory’s OHS Act that requires employers to take every reasonable precaution to provide a safe and healthy workplace and protect workers from known hazards. How do we know the general duty clause requires employers to protect workers from exposure to mould? Some provinces have specifically said so:

Express duty provinces. Four jurisdictions—federal, AB, ON and SK—have issued guidelines or bulletins on mould in the workplace in which they specifically say that their general duty clauses require employers to protect workers from exposure to mould. For example, SK’s guidelines on mould say that in a workplace, an employer has a duty to monitor worker exposure to substances that may be harmful, including moulds and mycotoxins.

Implied duty provinces. Four provinces—MB, NB, NS and QC—haven’t issued any guidelines that explicitly state that their general duty clauses require employers to protect workers from exposure to mould. But regulatory agencies in those provinces apparently imply the existence of such a duty even if they haven’t come out and said so. How do we know? These provinces have issued bulletins, hazard alerts or guidelines for employers on mould in the workplace and how to protect workers from exposure to it. These bulletins, alerts or guidelines generally say that exposure to mould in the workplace should be treated as a workplace hazard. The clear implication is that protecting workers from mould is required by the general duty clause. Also, by providing such bulletins, alerts and guidelines for employers, these provinces are strongly suggesting that employers have a duty to address mould in the workplace.

The other provinces and territories. NL, PEI and the three territories haven’t, to the Insider’s knowledge, specifically stated or implied that they consider employers under a legal duty to protect workers from exposure to mould in the workplace. And they haven’t issued any bulletins, alerts or guidelines on mould in the workplace. However, it’s likely that they would follow the same approach as the other provinces when it comes to workplace mould.

Insider Says: The Insider looked for but couldn’t find any court cases or administrative rulings holding an employer liable under OHS laws for failing to protect a worker from exposure to mould. However, we did find a report that indicated that a tribunal of the QC government, Bureau de Revision de la Commission de la Santé et de la Sécurité du Travail, had ruled in 1989 that a significant growth of the toxigenic mould Stachybotrys Chartarum in the workplace was a violation of the province’s OHS law. But we couldn’t find the actual ruling or confirm that it was ever issued.

Potential Consequences of Not Addressing Mould

Failing to protect workers from exposure to mould in the workplace can cause three kinds of problems:

  • Fines and regulatory penalties—although the Insider couldn’t find any cases in which employers were fined for failing to take steps to protect workers from exposure to mould, it happens in the U.S. all the time and it’s only a matter of time before such a prosecution occurs and a fine is handed down in Canada;
  • Work refusals—workers could refuse to do certain work for fear that they’ll be exposed to mould; and
  • Workers’ compensation claims—workers who get sick as a result of exposure to mould in your workplace may have viable workers’ compensation claims.


If you’re in a province like MB or SK that has issued detailed bulletins or guidelines on mould in the workplace, look to those bulletins or guidelines to determine your obligations. What should you do if your province or territory provides only very general information on mould in the workplace or no information at all? Answer: Look at what the other provinces require. Those requirements are likely to represent the standard judges, regulators and inspectors will use to determine what employers should do to protect workers from exposure to mould in all parts of Canada.

Requirements for protecting workers from exposure to mould vary from province to province. But in general, employers should take the following steps:

Step #1: Control Moisture in the Workplace

The best way to address mould in the workplace is to prevent it from growing in the first place. Mould is a microscopic organism that feeds off other organisms, living or dead, to grow. It thrives in environments that are rich in moisture. So if your workplace has recently sustained water damage, leaks, or flooding or is excessively humid, it’s a potential breeding ground for mould. To prevent mould growth, control moisture in your workplace by:

  • Monitoring humidity levels;
  • Promptly repairing any leaks;
  • Properly maintaining your HVAC system so that mould doesn’t grow in it and get blown throughout the workplace; and
  • Regularly cleaning carpets and other surfaces using HEPA-filtered or central vacuums.

Step #2: Risk Identification and Assessment

Assess the risk of exposure to mould in the workplace and determine if any mould is already present. MB has issued helpful guidelines that suggest employers:

  • Examine the building’s history, especially for prior flooding, leaks or water damage;
  • Speak to workers to see if they have any chronic health problems that may be mould-related, noticed any musty odours or have seen mould or water damage anywhere in the workplace;
  • Visually inspect the workplace for mould, water damage and leaks; and
  • Take samples of the air, possibly contaminated surfaces and any mould that’s discovered and have those samples tested to determine if mould is present and at what levels.

Step #3: Remediation

The presence of some mould in the air is normal. But if you discover high levels of mould in your workplace, you must take steps to “remediate” or eliminate it from the workplace. Mould remediation is tricky. Where the amount of contamination is small and on a non-porous surface, cleaning and disinfecting the area may be all that’s needed. But in other cases, it may be necessary to remove the contaminated material. And removing mould-contaminated material may inadvertently spread mould spores into adjacent areas.

Several provincial guidelines refer employers to the New York City Department of Health’s guidelines on mould remediation, which provide detailed procedures for mould remediation based on the size of the area affected. (The New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments are available at

If your mould problem is extensive, consider hiring a professional remediation consultant. Again, the MB guidelines list helpful information about what to look for when hiring a consultant. (See page X for a checklist of questions to ask prospective consultants.) If you don’t think you need professional help, use your own workers. But as the SK guidelines suggest, make sure that you provide workers with proper training on cleaning and removing contaminated materials, warn them of any risks associated with remediation work and give them appropriate PPE. You may also need to relocate workers who are vulnerable to mould-related illnesses or provide them with appropriate PPE during the remediation.

Step #4: Worker Education and Training

You’re likely to learn about mould problems in the workplace from workers who notice leaks or mould, or who develop illnesses that may be mould-related. So educate them on mould, the dangers of exposure to mould and the early signs and symptoms of mould-related illnesses. And encourage workers to come forward if they’re experiencing any signs and symptoms of a mould-related illness or if they notice mould or conditions that could lead to mould growth.


Toxic mould has been called the “organic asbestos.” But it hasn’t generated a flurry of lawsuits or OHS prosecutions in Canada. Still, brushing mould under the rug is a serious mistake. As an EHS coordinator, you need to impress on management the importance of protecting workers from exposure to mould. Taking steps to keep your workplace dry and mould-free can save you money and protect your workers from unnecessary and avoidable illnesses. And, if protecting the health of workers isn’t reason enough, as this article shows, taking steps to prevent workers’ exposure to mould can also protect your company from potential liability for OHS and other legal violations.



Here’s what your province or territory says about protecting workers from exposure to mould in the workplace:

FEDERAL: Guidelines recommend: a) Preventing mould growth before it occurs by controlling moisture, addressing leaks and adequately maintaining HVAC systems; b) Conducting mould inspections to establish the cause of any mould growth, assess the risk of adverse health effects on workers and building occupants and remediate the workplace; and c) Remediating the workplace by removing the mould and correcting the problems that lead to the mould growth [Fungal Contamination in Public Buildings: Health Effects and Investigation Methods, Health Canada,].

ALBERTA: Health and safety bulletin recommends: a) Cleaning, disinfecting and/or removing mould contaminated materials; b) Explaining the health risks to affected workers; c) If possible, isolating the source of contamination from the rest of the workplace to minimize worker exposure; d) Eliminating the moisture source; and e) Preventing mould growth by regularly cleaning carpets and other surfaces, promptly repairing leaks, properly maintaining HVAC systems, using HEPA-filtered or central vacuums and avoiding high humidity levels [Do I have a Workplace Mould Problem?, Work Safe Alberta,].

BRITISH COLUMBIA: Regulations require employers to investigate indoor air quality complaints by taking samples of airborne contaminants [OHS Regulations, Secs. 4.79(1) and (2)]. Guidelines for the regulations recommend: a) Investigating worker complaints about indoor air quality; b) Conducting a risk assessment of the potential for worker exposure to mould; c) Investigating mould contamination with visual assessments and sampling; and d) Preventing and remediating mould contamination [Guidelines, G4.79 Moulds and indoor air quality, WorkSafeBC,].

MANITOBA: Guidelines recommend: a) Investigating potential mould contamination by examining the building history, interviewing workers, conducting visual inspections and taking samples; b) Communicating to workers the potential health risks of exposure to mould and the steps being taken to remediate any mould growth; c) Remediating mould growth by cleaning or removing contaminated materials and addressing the cause of the mould growth; and d) Hiring a qualified consultant if necessary [Guidelines for the Investigation, Assessment, & Remediation of Mould in Workplaces, MB Dept. of Labour & Immigration,].

NEW BRUNSWICK: Pamphlet: a) Explains basic facts about mould, microbials and indoor air quality; b) Describes symptoms of exposure to mould; c) Gives signs of mould growth; d) Lists measures for controlling mould growth; and e) Spells out clean-up procedures for contaminated materials [Microbials and Indoor Air Quality, WHSCC,].

NEWFOUNDLAND/LABRADOR: No government guidelines or other information on mould in the workplace.

NORTHWEST TERRITORIES/NUNAVUT: No government guidelines or other information on mould in the workplace.

NOVA SCOTIA: Hazard summary: a) Notes that moulds and fungi are often implicated as a cause of poor indoor air quality; and b) Provides links to various resources on mould, including the federal guidelines mentioned above [Moulds and Fungi in Indoor Air, NS Dept. of Environment and Labour,].

ONTARIO: Hazard alert: a) Explains the health risks exposure to mould can pose; b) Explains the causes of mould growth; c) Recommends taking steps to prevent and remediate mould growth; d) Notes employers’ legal duty to protect workers from exposure to mould; and e) Provides links to resources on mould [Mould in Workplace Buildings, MOL,]. Guidelines recommend: a) Preventing mould growth by controlling moisture; b) Assessing the workplace through visual inspections and sampling to determine if there’s mould contamination; c) Remediating mould contamination, including removing contaminated materials, correcting the moisture problem, implementing special control measures to prevent worker exposure and the spread of mould from the contaminated areas to adjacent areas and relocating workers if necessary [Moulds: Workplace Guidelines for Recognition, Assessment, and Control, Occupational Health and Safety Council of Ontario,].

PRINCE EDWARD ISLAND: No government guidelines or other information on mould in the workplace.

QUéBEC: Task force report recommends: a) Identifying mould contamination by assessing the building environment with visual inspections and reviewing data, such as the building history and recurring and chronic health problems; b) Preventing mould contamination by controlling humidity and moisture, addressing leaks, providing proper ventilation and cleaning HVAC systems, humidifiers and dehumidifiers; and c) Remediating mould contamination by cleaning or removing contaminated materials and adjacent surfaces [Health risks associated with the indoor presence of moulds, Institut national de santé publique du Québec,].

SASKATCHEWAN: Guidelines recommend: a) Preventing mould problems by preventing and treating excessive moisture and maintaining HVAC systems; b) Determining if workplace has a mould problem by looking for signs of mould, water damage or musty odours and taking samples; and c) Cleaning up mould contamination by identifying and removing the source of the excess moisture and cleaning, disinfecting and/or removing contaminated materials [Facts About Mould, SK Labour and Health Depts.,].

YUKON: No guidelines or other information on mould in the workplace.

Checklist: 10 Questions to Ask When Assessing a Mould Remediation Consultant’s Qualifications

Here are 10 questions to ask prospective mould remediation consultants:

1. How many years of experience do you have?

2. Do you carry out this kind of work full-time or part-time?

3. What degrees or diplomas do you have?

4. How do you stay up to date with current developments in mould remediation?

5. What professional associations do you belong to?

6. Are you certified or registered by the Canadian Registration Board of Occupational Hygienists, American Board of Industrial Hygiene, Environmental Engineering Intersociety Board or provincial professional engineering association?

7. What equipment do you use?

8. What laboratories do you use to analyze your samples?

9. What insurance and bonding do you have?

10. What are the character and extent of reports that you prepare?

Tip: Also, get a list of the consultant’s recent clients and contact them for their opinion on the consultant’s services.

Source: Manitoba’s Guidelines for the Investigation, Assessment, & Remediation of Mould in Workplaces

Email This Post Email This Post


Like this article?

Please login at the top of the page or Click Here and register to read the rest of this article, and also access FREE whitepapers, sample policies, EC checklists, and so much more by taking advantage of our no obligation 3 issue FREE trial access to

Get answers to your toughest EC questions in Environmental Compliance Insider, Canada's one-stop resource for practical "how-to" help on managing environmental liability and due diligence.

Yes! Please start my subscription to Environmental Compliance Insider.

I understand that I can review everything risk-free. If I don't benefit from the "how-to" help in Environmental Compliance Insider, you'll refund the entire subscription fee.

Yes, I want the practical, plain-language Environmental Compliance help revealed in Environmental Compliance Insider. Click here to Order Now!

Read More about Environmental Compliance Insider

Like this article?