"Indoor Air Quality The Story of Mold: An Emerging
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.
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
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.
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
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
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
School boards, parent groups, manufacturers, material suppliers, and building
occupants have a raised level of awareness as to the cause and effect of
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
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.
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.