The interior of this furnace blower cabinet is soaked from a leaking condensate pan. The rusty sludge at the bottom was full of bacteria. (Copyright 2002, Jeffrey May, author of My House Is Killing Me!)
EDITOR’S NOTE:In this first installment of a three-part series,The Newsexamines the issues surrounding the certain types of mold and their relationship to HVACR systems. SinceStachybotrys chartarum has garnered the most media attention and has been linked to highly visible stories involving adverse health affects,The Newsis using this type of mold to exemplify the entire mold testing and remediation story.

It starts out from a leaky pipe, a potted plant, or a garment, to name a few sources. Then it begins to grow, in a stationary position, or through a release into the atmosphere. It is as old as life itself and people have lived in unison with it throughout history. It is also a threat to health and the quality of life — at least in some recorded instances.

It is mold.

The National Center for Environmental Health defines one type of mold, known as Stachybotrys chartarum, as a “greenish-black mold [that] can grow on material with a high cellulose and low nitrogen content, such as fiberboard, gypsum board, paper, dust, and lint. Growth occurs when there is moisture from water damage, excessive humidity, water leaks, condensation, water infiltration, or flooding. Constant moisture is required for its growth.”

The center describes the possible health affects of all mold species in buildings and homes in the following manner: “Mold exposure does not always present a health problem indoors. However, some people are sensitive to molds. These people may experience symptoms such as nasal stuffiness, eye irritation, or wheezing when exposed to molds. Severe reactions may include fever and shortness of breath. People with chronic illnesses, such as obstructive lung disease, may develop mold infections in their lungs.”

The key phrases are does not always present a health problem and may experience symptoms. In other words, exposure to mold may or may not cause an adverse health risk. However, erring on the side of caution is causing homeowners and building owners to take a second look at the effects of mold on indoor air quality (IAQ).

“Mold has only become problematic in the past 30 years as our antiquated building construction practices have continued despite epoch advances in materials and understanding of building behavior and science,” said Steve Bauman of Healthy Spaces LLC, Austin, TX. “The shift of the home from a place of safe haven to the role of cause of disease has its roots in the energy crisis of the 1970s.

“Since the onset of the energy crisis in the mid-1970s, the annual rise in the onset of asthma has risen at an alarming rate of increase in excess of 65% per year. This is directly attributable to the tight sealing of homes to save energy. Unfortunately, we’ve also ‘locked in’ all the indoor air pollutants.”

The recent high-profile jury trial of Dripping Springs, TX, homeowner Melinda Ballard thrust Stachybotrys chartarum, dubbed by some in the media as “black mold,” into the national spotlight. In June 2001 a jury awarded Ballard and her family $32.1 million in a case involving extensive mold damage to their home. The jury ruled that Farmers Insurance Group had improperly addressed Ballard’s water damage and mold claim and committed fraud in its handling of her claim.

“There is a great deal of money at stake and possibly human health,” said Bob Baker of BBJ Environmental Solutions Inc., Tampa, FL. “The fact that I have to say ‘possibly relative to health’ is the real problem. We have done pathetically little good research on the ‘mold problem’ in this country, so the vast majority of our knowledge base comes from media stories, completed litigation, case narratives, urban legend, and other similar questionable sources.”

Before a perimeter drain system was installed, water from a foundation crack soaked into the drywall. The insulation slowed drying, creating perfect conditions for Stachybotrys. (Copyright 2002, Jeffrey May, author of My House is Killing Me!)


There are many different types of mold and not all adversely affect human health. Some experts suggest that too much emphasis is put on the “most toxic” of all molds —Stachbotrys chartarum— and not enough on molds in general.

“Many other molds amplify nicely indoors and are capable of making people sick; and it doesn’t help to concentrate . . . on only Stachybotrys chartarum,” said Mike McGuinness of R.K. Occupational and Environmental, Phillipsburg, NJ.

(Note: Some in the media have broadly identified mold contamination as coming from “black mold.” The News recognizes that many types of mold are black, and not all of them cause health problems. However, the presence of any black mold is causing homeowners great concern. This is why our series focuses on mold testing in addition to remediation.)

“Most people don’t know that much about mold biology; in addition, the questions of what molds grow in a given environment and what potential impact they may have on health are extremely complex,” said Jeffrey May of J. May Home Inspections Inc., Cam-bridge, MA, and author of the book, My House is Killing Me.

According to May, there are thousands of different species of mold. Some produce poisons called mycotoxins — and are thus “toxic” — while others do not. Mycotoxins are generally found in highest concentrations in mold spores, he said.

“Whether or not a given mold species that can produce mycotoxins actually does so depends on the conditions, as well as the food upon which the mold is growing,” said May. “Therefore, while it’s difficult to make any blanket statement about the toxicity of a particular mold in a particular situation, Stachybotrys grows only on paper [including cardboard and drywall] and needs nearly saturated conditions.”

Identifying various mold species has been the undertaking of hygienists and scientists. The media’s concentration on “black mold” is an example of what the public is now just beginning to understand.

“With the advances in medicine today, I think we are finding more cause-and-effect relationships with indoor pollutants than we knew about 10 or 20 years ago,” said Jerry Wolf of Air Purification of Houston, Houston, TX. “As with any controversial subject like this, you always have those whom really do have a problem with mold and there are those who make themselves think they have a problem so they can sue someone else. Lack of education about mold and its effects is a big item that fuels the frenzy.”


In a home, one of the first areas to blame for mold growth is the ventilation system. After all, mycotoxins are likely to spread via a forced-air system. But does this system create a breeding ground for mold or are there other factors involving the system, such as an inadequately sized unit or poor maintenance practices?

“It is rare to find this mold in a heating system. The only exception that I know of is the paper filter frames in furnaces, where the condensate tray is overflowing and the filter is sitting in water,” said May. “Of course, in buildings with plenum returns and paper-containing ceiling tiles or drywall under roof leaks or sweating pipes, contamination of the air with Stachybotrys chartarum toxins is a possibility.

“Other potentially toxic molds that can be found growing directly in heating and cooling systems — and even in the dust on baseboard convectors that are installed close to concrete or below-grade near foundation walls — include penicillium and aspergillus species.”

Bauman added that a necessary component for the growth of bacteria, mold, and fungi is the presence of heat, usually associated with temperature differentials found between attics and living spaces, “and the poor insulation around the penetrations, particularly of the HVAC system.”

Meanwhile, Wolf said the culprit could be a poorly sized system.

“We have seen many cases where mold is literally growing on walls in a home because the humidity is too high,” he said. “The homeowner decides to upgrade from a 3- or 4-ton A/C because it will cool better. They don’t realize that the system will cool the house so fast, it doesn’t run long enough to dehumidify the air in the house. Or, maybe they put in a larger system but didn’t increase the filter size and now they are restricting the airflow and the coils ice up.

“We’ve seen many cases where their filtration was so poor the coils trapped more dirt than the filter did! These problems all help put moisture in the air and we know mold loves it.”

Of course, many HVACR contractors believe that some mold problems are the result of building maintenance issues, like a leaky roof or other design and construction problems, as opposed to HVAC.

“On the other hand, I am just as sure that there are other mold issues that the simple maintenance of equipment and humidity control might cure,” said Steve Miles of Jerry Kelly Heating and Air Conditioning, St. Charles, MO.

Whether an HVACR system delivers mold spores or contributes to their growth is determined on a case-by-case method. How HVACR contractors respond to the need to prevent and eradicate mold could be a key to many happy and healthy customers — and a possible new source for profits.

Part 2 of the series will explore factors that affect mold growth, the products and services designed to prevent or eliminate mold growth, and how experts are advising homeowners on the mold problem. Part 3 will examine how this new initiative to inform and aid consumers could possibly be a new profit center for trained and educated HVACR contractors.

Publication date: 06/24/2002