Changing the way the world builds - Greener. Smarter. Faster.
Modular Construction
MBI members receive discounts, leads, free publications, and much more.





Laurie Robert

"Indoor Air Quality The Story of Mold: An Emerging Issue"
 by Laurie Robert, NRB, Inc.

If you sat through any of the IAQ presentations at MBI's Midwest or Western regional meetings last year, or at the annual convention in March in Orlando, chances are you are somewhat familiar with the ongoing story of mold found in portable classrooms. What follows is both a recap and an update of events that have ultimately altered a market and raised levels of awareness of a new and emerging IAQ concern.

FungusFrom Reaction to Proaction
In 1998, indoor air quality issues were identified as the possible cause of varying health reactions in a few students housed in portable classrooms in the Province of Ontario. Through a series of investigations, it was ultimately determined that a slimy black-green substance existed, hidden mostly within the wall and roof cavities of a number of portable classrooms. The substance was sent away for testing and identified as Stachybotrys atra--a relatively uncommon species of mold that produces toxigenic spores.

Soon after this discovery was made public, parent groups rallied, and school boards were compelled to take immediate action. The issue attracted the keen interest of the media, instigating a 20 minute news documentary which alleged a potential link between this particular mold, portable classrooms, and an associated health risk for children. What followed was a newspaper article or a story on the evening news seemingly every few weeks for the better part of a year.

Although the suspected health risks were initially speculative, most school boards took positive action, ranging from cursory inspections through to invasive testing. The process of the latter involved fully qualified personnel, in protective clothing and respirators, with tents and filtering systems, removing interior and exterior finishes almost completely. Any contaminated materials uncovered were removed in accordance with a New York City Protocol established in 1993. (If one can imagine people in impermeable white suits with respirators working in and out of portable classrooms, on school properties visible to the public, one might appreciate the growing public apprehension.) The cost to the school boards to inspect and remediate these classrooms was in the tens of millions of dollars.

By definition, mold is a fungal infestation that can cause the disintegration of a substance. For that reason alone, it is not something that should be neglected if discovered. While Stachybrotrys atra may have been in existence "forever," it quickly became a new buzz phrase in the IAQ domain. The initial reaction to the link between mold and a health risk was that mold is a relatively common occurrence, found on everything from food to tile grout to damp building basement walls. It seemed inconceivable that not only was this substance now being tagged as a potential serious health threat, but it was being introduced as one specific to portables.

Since first obtaining knowledge of this problem less than two years ago, we have taken the opportunity to review and consider aspects of the design, construction, use, life expectancy, and the very important ongoing operation and maintenance program of a portable classroom. We met with school boards and parent groups, attended conferences and seminars by building envelope and environmental experts, and looked at reports issued by health departments.

MoldSo Why is Mold an Indoor Air Quality Problem?
When we think of IAQ issues in any sort of building, we tend to think in terms of "sick building syndrome," a condition often identified with "tight" buildings. Elevated carbon monoxide levels, volatile organic compounds such as formaldehyde or benzene emitted from some construction materials, carpets and glues, or generally poor ventilation issues account for many of the IAQ environmental problems found today. Unlike some of these other types of environmental problems that may be rectified by the proper introduction of fresh air, mold is a growing organic substance that must be physically removed. Even dead, biological amplification sites can release spores into the air.

At one time, mold was considered more of an aesthetic problem than one of health, and while some molds may be generally harmless, others may be considered extremely toxic. According to reports obtained from a number of websites, including the Environmental Protection Agency, stachybotrys atra has been associated with a range of health problems, and even deaths in Cleveland, Ohio. Although research and tests are currently being conducted at an increased rate, there are seemingly few documents, regulations, or guidelines assessing potential risk levels from exposure. Depending on the size of the amplification site present, the type of species and the sensitivity levels of the individuals, exposure to concentrated levels of some types of mold spores may lead to a variety of symptoms ranging from a runny nose to other more potentially serious illness.

We may not be certain if human beings are more sensitive to mold today than we were hundreds of years ago, however it has been suggested that our rate of exposure may be higher in part due to the choices of building materials used today. Common building products containing high cellulose and low nitrogen content are a natural target for mold spores when moisture is present.

According to reports, most fungi require a surface relative humidity (RH) level of 80%. However, some can grow on surfaces with as little as 65% RH. Material that is wet from a localized water source (a spill, plumbing leak, roof leak, wet washing of floors) may be considered at 100% RH level. So spills, leaks, even wet washing of floors that allow moisture to penetrate organic building materials must be repaired and dried quickly.

Large surfaces of organic material, such as the paper on drywall, offer an ideal source of food while lumber is not quite as susceptible to infestation. Some types of batt insulation, although not a natural nutrient base, can collect dust, dirt, and moisture that support biological contamination. In addition, acoustical ceiling tiles, carpet backing, dirty ventilation ducts or pans, or even counters and cabinets can be potential hosts if unwanted moisture remains present.

FungusSo, What is the Current Status?
Begin with a portable classroom environment that has typically been maligned as an unsuitable environment for learning for years, add an implied related health risk from an new source, and you have the blueprint to significantly change how portable classrooms are specified, built, purchased, and operated.

It is important to understand that mold spores are a natural part of our environment. We cannot control their airborne movement, so we have to look at all the factors that combine to create the environment they need to grow: moisture, temperature, and the nutrient base.

In the Province of Ontario, most individual school boards have implemented their own design and specifications for many years. Variations in construction methods and materials are common and the distinctions between designs are generally motivated by selective approaches to aesthetics, energy efficiency, maintenance issues, longevity, and comfort levels--all generally combined with price sensitivity.

The aftermath of cleaning up hundreds of portables, at a cost of millions of dollars, has ultimately changed what is designed, built, and purchased in Ontario today. For example:

  • School Boards who have typically issued their own specific designs have revisited methods and materials, and most have made changes--some subtle, many considerable--in an effort to deal with the possibility of eventual microbial contamination.
  • School boards, parent groups, manufacturers, material suppliers, and building occupants have a raised level of awareness as to the cause and effect of microbial contamination
  • There has been a discernible reduction in the bid/purchase of portable classrooms in the year 2000, a result of additional government funding available for new schools and additions, perhaps supported by a reluctance to add more portables to the system.
  • Performance specifications that have been written in 2000 contain specific conditions requiring classroom designs reflect methods and materials that are resistant to mold growth.
  • Many designs have changed to steel framing, almost all have replaced standard drywall with an alternative "paperless" gypsum product, and most include the HVAC packages required for the proper control of relative humidity.

One very important outcome over the past eighteen months is that the media and public alike have acknowledged that toxic mold is a problem in any building environment under the right conditions--not just portables. In fact, the same television program that offered the 20 minute connection between mold, portables, and health did a follow up segment almost a year later which said that this same problem is prevalent in all types of buildings today!

As a manufacturer, our company has witnessed a complete paradigm shift in the portable classroom market in this region in less than two years. In general, school boards understand that there will always be a need for the instant and flexible space a portable classroom can offer. While there may be less in number today, these new IAQ concerns have prompted most school boards to overwrite "price sensitivity" with "environmental sensitivity" in their current classroom designs!

The current status is just that--current. IAQ problems are quite simply a moving target. For every possible solution that may be developed, another IAQ issue may begin. Raised levels of awareness and education are paramount in just trying to keep up.

As a member of the MBI and the commercial factory-built industry, you are encouraged to become aware of the IAQ issues that surround you. Look at your geographical area and the potential effects of your own climatic conditions. Look at the use (or misuse) of portable classrooms in your region. What is the purchasing mechanism? How good and consistent are the operation and maintenance programs that are implemented? Both short and long term maintenance is key in ensuring that buildings remain moisture free.

Certainly not everyone will experience an outbreak of toxic mold, but indoor air quality and indoor environmental quality have made it to one of the top ranked concerns of the EPA. You could choose to ignore these IAQ issues, you could consider them a threat to your business, or you could think about them as an opportunity to learn and implement change.

Laurie Robert is vice president of sales and marketing at NRB, Inc. in Grimsby, Ontario, Canada.  She also serves on the board of directors as MBI's vice president and often speaks for MBI on the issue of indoor air quality.

Footnote: All information in this article pertaining to facts about mold or other IAQ issues in general are excerpts of data obtained from outside sources including: environmental and building envelope seminars, environmental reports (focusing on microbial contamination), the U.S. Environmental Protection Agency (Including the Indoor Air Quality Information Clearinghouse), as well as the American Industrial Hygiene Association.

Copyright © Modular Building Institute, July 2000.