Mould
A Basic Guide
Summary
Mould is a fact of life. Moulds will grow practically
everywhere people live and work. Mould is recognized
as an occupational hazard for indoor workers as well as
outdoor workers who work in warm and humid
environments. All moulds are not harmful. However
certain types of moulds can cause adverse health effects.
Occupational health and safety legislation does not
specifically address adverse health effects of mould
exposure. Mould growth within buildings is not
acceptable and prompt remediation is necessary.
Mould contamination can affect building components
such as walls, floor coverings, windows, ventilation
systems, and support beams that are likely to be moist
or water damaged. Mould may grow in warm and wet
areas such as bathroom tubs, between tiles and window
frames.
There have been reports linking health effects to mouldy
surfaces in persons who worked in contaminated offices.
Symptoms such as fatigue, respiratory ailments and eye
irritation were typically experienced in these cases.
All exposed people are not affected. Individuals with
compromised immune systems are at the greatest risk.
In recent years potential adverse health effects of mould
have caused widespread concern. Short-term effects of
mould exposure include allergy-type symptoms such as
runny nose, cough, and sore throats. This guide provides
an overview that will help you recognize, evaluate and
control mould exposure in the workplace. Topics covered
include: a description of moulds; health effects of mould;
what to do when mould is found; how to interpret mould
measurement data; how to clean up mould; and how to
prevent mould growth.
Table of Contents
Section I Types and Causes of Mould
1. What are Moulds? . . . . . . . . . . . . . . . . . . . . 2
2. Causes of Mould Growth . . . . . . . . . . . . . . . 4
3. Types of Mould . . . . . . . . . . . . . . . . . . . . . . . 5
4. How Moulds Grow . . . . . . . . . . . . . . . . . . . 10
5. Where Moulds Grow . . . . . . . . . . . . . . . . . 11
Section II Health Effects of Mould Exposure
1. Difficulties Linking Health Effects
to Mould Exposure . . . . . . . . . . . . . . . . . . . 14
2. Common Health Effects of
Mould Exposure . . . . . . . . . . . . . . . . . . . . . 15
Section III Mould Problems in the Workplace
1. Why Be Concerned About Mould? . . . . . . . 20
2. Who Should Be Concerned About Mould? . 21
3. Knowing if Your Workplace Has a
Mould Problem . . . . . . . . . . . . . . . . . . . . . . 21
4. Air Sampling and Laboratory Analysis . . 27
5. Employee Health Survey . . . . . . . . . . . . . . 29
Section IV Dealing with Mould
1. If You Suspect Mould . . . . . . . . . . . . . . . . . 34
2. When Mould is Found . . . . . . . . . . . . . . . . . . . 35
3. Controlling and Mitigating
Mould Growth . . . . . . . . . . . . . . . . . . . . . . 37
Section V Interpretation of Mould Measurement Data
1. Comparing Mould Measurement Data
with Standards . . . . . . . . . . . . . . . . . . . . . . 40
Section VI Mould Clean Up and Prevention
1. Why Clean Up Mould? . . . . . . . . . . . . . . . 44
2. General Guidelines for Mould Clean Up . 45
3. Mould Clean Up Methods . . . . . . . . . . . . . 47
4. Knowing When the Mould Remediation
or Clean Up is Finished . . . . . . . . . . . . . . . 55
Section VII Water Damage
1. Water Quality . . . . . . . . . . . . . . . . . . . . . . . 58
2. Cleaning Up Water Damage . . . . . . . . . . . 59
3. The Water Clean Up Process . . . . . . . . . . 64
Section VIII Preventing Mould Growth
1. General Procedures for All Workplaces . 66
2. Specific Measures for Construction
in Hospitals . . . . . . . . . . . . . . . . . . . . . . . . . 68
Section IX Standards, Guidelines and Protocols for Mould
1. Standards, Guidelines and Protocols for
Mould . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Section X Occupational Health and Safety Legislation
1. Canadian Sources of Indoor Air
Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . 76
2. Canadian OH&S Legislation . . . . . . . . . . 77
3. US OH&S Legislation . . . . . . . . . . . . . . . . 83
Section XI Information Sources
1. Canadian Government Departments
with Responsibility for Occupational
Health and Safety . . . . . . . . . . . . . . . . . . . . 86
2. US Federal Safety and Health Agencies . . . 91
3. State Occupational Safety and
Health Plans . . . . . . . . . . . . . . . . . . . . . . . . 95
Section XII Appendices
A1. Mould FAQ . . . . . . . . . . . . . . . . . . . . . . . . 104
A2. Case Studies . . . . . . . . . . . . . . . . . . . . . . . 110
A3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 116
A4. Mould Problem Reporting Form . . . . . . 117
A5. References . . . . . . . . . . . . . . . . . . . . . . . . . 118
Introduction
The guide will provide an overview of mould related
workplace issues and enable a reader to:
鈥? recognize mould and the conditions which are
favourable to its growth;
鈥? understand how people might be effected by
mould exposure;
鈥? access guidelines and regulations;
鈥? identify jobs that can potentially pose a risk of
harmful mould exposure;
鈥? plan workplace mould surveys;
鈥? understand when mould measurement and
analysis are needed;
鈥? interpret information from mould measurement;
鈥? understand how to clean up mould; and
鈥? develop and implement a mould management and
control program.
For many years, moulds have been recognized as
potential health hazards in some specific workplaces.
For example, workers in construction and demolition
operations have become ill after exposure to dust
containing mould. In recent years, there has been
increasing concern about mould related health effects
due to incidence of mould related complaints in:
鈥? schools (specially in portable classrooms);
鈥? residences for senior citizens; and
鈥? office buildings with indoor air quality problems.
2. Causes of Mould Growth
Mould needs two factors to flourish and grow 鈥?
moisture and food (nutrient). Mould growth can start
in any building where the following events have
occurred:
鈥? flooding,
鈥? water leaks,
鈥? inadequate air exchange,
鈥? excess humidity, or
鈥? condensation, especially in winter, on poorly
insulated surfaces.
Sources of Indoor Moisture that Can Cause
Mould Problems
鈥? floods,
鈥? backed-up sewers,
鈥? leaky roofs,
鈥? humidifier which is not regularly cleaned and
disinfected,
鈥? damp basements or crawl spaces,
鈥? plumbing leaks,
鈥? house plants and their debris,
鈥? steam from cooking and showers, and
鈥? wet clothes hung to dry indoors.
Mould can use a wide variety of material as food
(nutrient). These can be organic materials such as
wood, paper, leather, fabric, etc., or inorganic
materials such as grout, painted walls, cement, plaster,
etc., where moulds can get nutrients from dust and
soil particles.
Since these materials are often part of the structures
in which we work, we cannot effectively remove them
to prevent mould growth. Our first line of defense
against mould growth is to prevent excessive moisture
and dampness.
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Sample
VISUAL MOULD INSPECTION CHECKLIST
Date: ________________ Location: _______________ Inspected by: _______________ and _________________
OBSERVATION
RECOMMENDATION(S)
INSPECT LOOK FOR Needs Further Action
No Yes
Ventilation system Damp filters/insulation __________________________
Damp conditions __________________________
Overall cleanliness __________________________
Ceiling tiles, exposed Signs of leak __________________________
insulated pipes Dampness __________________________
Unusual patches/stains __________________________
Gypsum wallboard Dampness __________________________
surfaces Unusual patches/soiling __________________________
Degraded wall surfaces __________________________
Mould under wall paper
and wall coverings __________________________
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3. Controlling and Mitigating Mould Growth
Controlling moisture is the key to preventing indoor
mould growth. The relative humidity of indoor
environments should be maintained at 20鈥?40% in
winter and no more than 60% the rest of the year.
Excessively dry air can also cause adverse health
effects. If and when moisture problems develop, rapid
and appropriate responses are important to prevent
mould spores from germinating (see sources and
strategies below). If wetness or spills are dried within
24鈥?48 hours, mould growth is less likely to occur.
Eliminating Possible Sources of Excessive Moisture
Indoor sources
FIX plumbing leaks, drips or 鈥渟weating鈥? pipes.
LIMIT sources of indoor humidity/dehumidify
indoor air.
IMPROVE air movement in poorly ventilated areas.
INCREASE fresh air ventilation when outdoor air
is not humid.
INSULATE areas where dampness or condensation
can occur.
WARM cold surfaces where condensation may occur.
Outdoor Sources
MAINTAIN roof and gutter/downspout system.
DIRECT runoff away from foundation by grading,
draintile, landscaping, etc.
USE air conditioning and keep building closed during
high outdoor humidity.
PREVENT leakage around windows, doors, flashing, etc.
WATERPROOF foundations.
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Level IV 鈥? Extensive Contamination
(Greater than 100 contiguous sq. ft. in an area)
(10 m2)
A health and safety professional with experience
performing microbial investigations should be consulted
prior to remediation activities to provide oversight for
the project. The following procedures are recommended:
a. Personnel trained in the handling of hazardous
materials equipped with:
i. Full-face respirators with high efficiency
particulate air (HEPA) cartridges.
ii. Disposable protective clothing covering
both head and shoes.
iii. Gloves.
b. Containment of the affected area:
i. Complete isolation of work area from
occupied spaces using plastic sheeting sealed
with duct tape (including ventilation ducts/
grills, fixtures, and any other openings).
ii. The use of an exhaust fan with a HEPA filter
to generate negative pressurization.
iii. Airlocks and decontamination room.
c. Vacating people from spaces adjacent to the work
area is not necessary but is recommended in the
presence of infants (less than 12 months old),
persons having undergone recent surgery, immune
suppressed people, or people with chronic inflam-
matory lung diseases (e.g., asthma, hypersensitivity
pneumonitis, and severe allergies).
d. Contaminated materials that cannot be cleaned
should be removed from the building in sealed
plastic bags. The outside of the bags should be
cleaned with a damp cloth and a detergent solution
or HEPA vacuumed in the decontamination
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2. Cleaning Up Water Damage
A wide variety of materials can be water damaged and
may need to be cleaned. This includes furniture, carpets,
textiles, books, files and papers, ceiling tiles, wall
paneling, plaster, vinyl, hardwood floors, concrete
floors, fiberglass, etc. The types of cleaning required
for various water-damaged materials are summarized
on the following pages.
General Guidelines for Cleaning Up Water Damage
USE controlled conditions that prevent dispersion
of any contaminants to other areas of the building.
ISOLATE the area and use negative air pressure where
the work is proceeding so that clean air from
surrounding rooms is drawn towards the work area
(rather than having debris and dust from the work
area dispersed to other parts of the building).
REMOVE debris and wet materials with care, sealing
them in bags and covered containers. Once outside
the building discard these materials as normal
construction waste. Clean all equipment used inside
the 鈥渉ot鈥? zone before removal.
ASSUME a hazard unless it is proven that a hazard
does not exist. Wear personal protective equipment:
eye protection, gloves, boots, disposable coveralls
and appropriate respiratory protection.
A flow chart showing the clean up process is shown
on the following page.
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