Remodeling 1: Mold and What to Do About It

While answering a question from a member on the subject of mold in her home, I came upon this article written in March 2001 by the Workplace Safety and Health Division, Manitoba Department of Labour & Immigration, Canada. This article tells it all, so I want to share it with you. Keep in mind that this report is mainly for contamination in large commercial buildings; however, information contained in this report can be helpful if problems arise in your own home as well as the office.

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Introduction to Mold

What is Fungi or Mold

Fungi are primitive plants that lack chlorophyll and therefore must live as parasites or feed on organic matter that they digest externally and absorb. The true fungi include yeast, mold, mildew, rust, smut and mushrooms. They usually grow best in dark moist habitats, and are found wherever organic matter is available. Some fungi can grow under extremely difficult conditions. This section discusses those fungi known as molds (sometimes spelled moulds). Humid or damp conditions in the home, school or workplace may promote the growth of molds, as well as bacteria and dust mites.These organisms may contribute to poor indoor air quality and can cause health problems.

Fungi in indoor environments comprise microscopic yeasts and molds, known as micro fungi, while plaster and wood-rotting fungi are referred to as macro fungi because they produce sporing bodies that are visible to the naked eye. Apart from single-celled yeasts, fungi colonize surfaces as a network of filaments, and some produce numerous aerially dispersed spores and other chemical substances such as volatile organic compounds (VOC's). The naturally occurring substances produced by fungi that bring about a toxic response are called mycotoxins, and are usually contained in the spores. Toxicity can arise from inhalation or skin contact with toxigenic molds.

Health Effects

In most non-contaminated workplaces the possible mold exposure would not be expected to present a health hazard except to very susceptible individuals. In contaminated situations the risk from exposure to mold increases. Reactions are varied and complex depending upon many factors. Human factors include personal susceptibility, route of exposure, age and state of health. Mold related factors include amount and length of time of exposure, virility and viability of the organism, and whether the effect is infection, allergenic, toxigenic or some combination of these. The effects of inhaling mold spores include allergies, infection or irritation.

  • Allergic reactions - a significant portion of asthmatics are allergic to molds, so that exposure can bring on attacks. Other forms of immediate and delayed allergic responses, such as hayfever (allergic rhinitis), also may occur.
  • Toxic and Irritative effects - long-term exposure to molds has been associated with a number of non-specific respiratory and flu-like symptoms, headaches, skin problems and impaired immune functions as well as a lung condition in infants known as pulmonary haemosiderosis.
  • Infectious mechanisms - in immuno-compromised individuals, exposure to molds that would not normally cause illness can result in infection, termed mycosis. Under certain conditions, molds can pose a health hazard. Factors that increase the risk of illness include:
    • Susceptible individuals - those allergic to mold, those with low immunity and babies whose lungs are not completely formed.
    • High levels of exposure - exposure to large numbers of spores over a long period of time.
    • Species of mold - the more noxious molds (high potential for mycotoxin production) pose the greatest risks.

Not surprisingly, young babies, asthmatics, and persons who have poor immune systems (such as those undergoing cancer treatment and persons with HIV) are at the highest risk if they are exposed to large amounts of mold. However, although effects of molds on the general population are yet less well known, this does not suggest that mold growth indoors should be left alone. Mold in occupied buildings should always be kept to a minimum.

Molds of Health Concern

Indoor air contains spores and filaments of many different molds but the most common are likely to be species of Cladosporium alternaria and other mold typically also found in the normal outdoor environment. However in "sick buildings" one can find toxigenic or allergenic mold, including certain species of Penicillium, some Aspergillus, Stachybotrys and Fusarium. Most mold found in indoor air are able to obtain the nutrients they need from dead moist organic material. Wood, paper, surface coating such as paint, soft furnishings, soil in plant pots, and drywall can provide ample opportunity for mold to grow.

Investigating Potential Contamination

What triggers an investigation for mold contamination

An investigation for mold contamination can be triggered by adverse health concerns of occupants, observations of growing mold, unusual odours, or events of water intrusion. A variety of symptoms or observations, such as respiratory problems, headaches, nausea, irritation of eyes, nose, or throat, tiredness, fatigue, etc may trigger an investigation into potential mold contamination. Mold may be observed on walls, pipes, ceiling tiles, window ledges, books, files, documents, etc. Musty odours and other unusual smells may indicate potential mold contamination. Also, any indication of water intrusion, flooding, condensation or high humidity, especially if chronic and or severe suggests potential mold contamination. In most instances the precipitating factors for an investigation into mold contamination are a combination of occupant adverse health symptoms combined with a history of water intrusion. When mold is visible, maintenance or housekeeping staff normally clean it and remove it; i.e. visible mold is treated as "you see it, you get rid of it". Odours can arise from many sources, but in the absence of supporting evidence (e.g. occupant health complaints or an IAQ investigation that excludes other options) odours alone do not a trigger a mold investigation.

The building history

The mold investigator examines a building's history looking at the original design, original intended use, construction (materials, workmanship, location), and any renovations or additions. This information is examined for changes that point to potential opportunities for mold (or other biocontaminants) to colonize. Present use vs. the intended use When the present use of a building is different from the intended use, the original building design may not be suitable. For example, a basement area that was not intended for storage is often used to store old files and documents. Since the design did not intend the basement area to be ventilated and kept dry, when water enters or the humidity is elevated the conditions are perfect for mold to grow on these materials. Similarly, when a basement not intended for occupancy is converted to office space the occupancy of that basement can generate both high humidity and nutrient material for mold to grow. Another example, when office dividers and walls are erected and then occupancy is increased, the original HVAC system may be inadequate. Condensation and poor air circulation that results can lead to conditions for mold to grow. Probably the most significant change in building design to affect conditions fostering mold growth came from the demand over the past 25+ years for greater energy efficiency. This change resulted in many buildings having HVAC systems that were not designed to handle the excessive moisture that develops in these energy efficient buildings. The high humidity that results can lead to hidden mold growth in many parts of the building, and this growth is extremely hard to find because there may be no signs to indicate its presence.

Present state of construction or deterioration

As structures age they deteriorate; a building envelope begins to break down and if proper maintenance is not practiced the interior of the building becomes subject to intrusion of the elements, most notably water. When this occurs, biocontamination is likely to follow. An older building with apparent deterioration may require the services of a building engineer to conduct a thorough building envelope investigation. The results of this investigation can indicate where moisture may have entered and consequently where mold may grow.

The mold investigator should check the following:

    Building exterior:
  • Windows, doors, air conditioning units, dormers etc - is the paint peeling or blistering, is there rot or other damage that might allow water to penetrate.
  • Roof - is there damage that could allow water to leak in.
  • Exterior walls - are there breaks, cracks or other openings.
  • Joints at corners, top sills, side jambs, and where different claddings meet must be examined for continuous caulking that seals the joint properly.
  • Basement window wells must be examined for proper drainage (gravel and drain tube to base of wall is normal) and to be sure they don't leak.
  • Basement walls should be examined for cracks or other damage that could indicate water intrusion sites.
  • Drainage pipes (e.g. rain-trough down spouts) should be examined for damage or blockages that might lead to water entering the building.
  • Pipes that penetrate the basement wall (e.g. utilities) should be checked for proper seals.
  • Slope of ground around basement wall must provide proper drainage.
  • Drainage holes, pipes for water that might collect behind exterior veneer must not be blocked.
    Building interior:
  • Basements should be examined for renovations that might trap condensation, evidence of leaks around pipes that penetrate the wall, leaks around windows, condensation around cold spots or on plumbing pipes, plumbing leaks (water and sewage pipes, appliances), HVAC system, standing water (e.g. sewers, sumps, and puddles) active ventilation of the area, leaks from the floor above, relative humidity, materials that might sustain growth in high humidity, expansion joints at floor-wall junctions.

Present environment of building

A building's environment provides clues to potential mold contamination - usually these clues are water related. For example, high humidity, condensation around windows, in corners or on plumbing, stained ceiling tiles, blistered paint, peeling wallpaper, rotted wood around windows or near plumbing, mildew or mold in bathrooms, water stains around sinks (kitchens, lunchrooms, janitorial storage rooms, water in crawl spaces or basements, and leaks. Also, odour may indicate mold - many molds produce odours that are readily detectable. Activities in the building can contribute to mold growth; e.g. activities that generate moisture (fountains, showers, etc), accumulation of left over food, temperature below the dew point, and HVAC system that does not supply sufficient fresh air.

Impact of renovations or additions

Whenever an existing building is renovated or has a structure added, then opportunities occur for mold to grow. New components joined to old ones may not react to environmental changes in the same manner, and two structures may shift or settle separately. Components can work against each other causing separation and damage. When new internal structures are erected they can impede the HVAC system's ability to provide sufficient air supply or movement thus potentially creating conditions for mold to grow. There are certain kinds of mold contamination not readily detectable by the methods discussed in this report. If unexplained sick building syndrome symptoms persist, consideration should be given to collecting dust samples with a vacuum cleaner and having them analysed for fungal species. Recommendations have also been established for bulk samples of the inside of ventilation ducts.

Biocontamination Remediation Procedures


In all situations, the underlying cause of water accumulation must be rectified or fungal growth will reoccur. Remediation performed without first identifying and rectifying the cause of the biocontamination will result in a regrowth of the mold. Emphasis should be placed on ensuring proper repairs of the building infrastructure so that water damage and moisture buildup does not reoccur. Water infiltration should be stopped and cleaned immediately. An immediate response (generally within 24 to 48 hours) and thorough clean up, drying, and/or removal of water damaged materials will prevent or limit mold growth. If the source of water is elevated humidity, relative humidity should be maintained at levels below 40 - 60% to inhibit mold growth. It must be clearly understood that porous materials, such as furniture, ceiling tiles, plaster/lath, gypsum wallboard, similar building materials, and carpet, that have been become wet due to floods, roof leaks, sewage backup and groundwater infiltration should be discarded. Only in exceptional cases, and within 24 to 48 hours, should these materials be considered for drying and disinfecting. Special procedures are required for the restoration of books and paper. Professional conservators should be contacted for information on handling these types of wet products. The effectiveness of any remediation of contaminated porous material must be evaluated as a standard procedure in all abatement activities. Surface sampling is advisable on porous material adjacent to the removed contaminated material. All positive results in excess of background levels should be evaluated by a technically qualified person to determine whether additional remediation is warranted. The effectiveness of any remediation of contaminated building materials (plaster, drywall, roofing material, etc.) should also be performed. A follow-up evaluation should be performed in the remediation area after approximately three to six months to ensure that the growth of mold has not reoccurred. This follow-up evaluation may be air testing and/or surface testing, as appropriate.

Hiring a Consultant to Help

It is possible that, after evaluating the information in this document, you will not be able to resolve the situation by yourself. If this is the case, you will need to bring in some expertise to help you resolve your biocontamination problem. As there are no legal restrictions on who can offer their services as a biocontamination investigator, and it will be up to you to ensure that they are qualified to do the work before you hire them. The following is intended to assist you to find a qualified consultant.

Where Do You Look?

There are several sources one can check for information and the names of consultants available locally. Contacting professional associations and public service organizations related to occupational safety and health is a good place to start. These organizations include the Canadian Registration Board of Occupational Hygienists, the American Industrial Hygiene Association, and the Manitoba Association of Consulting Engineers. Another useful source can be the consultants listing in the Yellow Pages of your phone book. Finally, there may be a university, college, or hospital in your area that has an occupational or environmental health program. Their staff professionals are often available for consultation.

Defining the Work to Be Completed

Once you have found one or more consultants who can do the work, you will need to define the type of work to be completed. One of the best tools to accomplish this task is to have the consultants prepare a project proposal for your review. Often, in a larger job, proposals from several points of view are evaluated and used as one of the bases for the final selection of the consultant. In this case, answers to pertinent questions in the preceding section may be sought in the proposal rather than in the interview. Aside from background qualifications of the consultant, the proposal should answer the following questions:

a) How much is the service going to cost? Smaller jobs are often bid on an hourly basis, typically with a minimum of one-half day's work, plus direct expenses commonly specified. Larger jobs are usually bid at a fixed amount, based on the work steps described.

b) What is the consultant going to do? The answer to this question may range from a simple agreement to study the problem to a comprehensive step-by-step plan to solve it.

c) What will be the end result? The answer to this question is all too often not clearly understood; the result is usually a report that specifies the consultant's recommendation. If you do not want to pay for the preparation of a written report, and a verbal one will do, specify this in advance. As recommendations often call for construction to be carried out by others whose work is not subject to the consultant's control, results usually cannot be guaranteed. Rather, an estimate of the results to be attained is all that can be expected.

Thanks again to the Workplace Safety and Health Division, Manitoba Department of Labour & Immigration for such a thorough report. My following article, Moisture and Humidity Problems in the Home touches on some of these problems in the home and offers some solutions as well.


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