By Bob Baker

I just returned from a week in the upper Midwest. During this hectic trip which included visits to Cleveland, Chicago, and several cities in central Michigan, I was reminded of a series of debates that are taking place more and more frequently: "Are mold problems greater in the north or south?" I'm not sure why it is so important that we establish which part of the country has the biggest and "baddest" problems. Possibly this has something to do with the natural competitive spirit of Americans. We can leave that to the psychologists. We can limit our attention to what all this means in reference to indoor air quality and the services we provide to our customers.

Mold, Fungi, or?

First, it may be helpful to get some terms straight. We see and hear a lot about mold. As they say, it gets "all the press". Actually mold is one of several one-cell plant like organisms that are broadly classified as fungi. It is helpful to realize that when we hear about a "mold growth"; it could actually be mold but is probably several different species of fungi.

Bacteria are also small (micro) organisms that contribute to contamination of air-conditioning systems. Bacterial growths account for most of the slimes that clog drain pans and block drain lines. These lead to the overflows that do so much damage. In addition, bacteria are responsible for the initial sticky coating on heat transfer surfaces that catch and hold dust and fibers and lead to the eventual clogging of coil passages. Bacteria also provide a source of food for many types of fungi.

Viruses also get a lot of attention because they are responsible for so many medical conditions. Viruses cause colds, flu, and a number of far more serious diseases. Also viruses can travel through the air and so can be distributed by air-conditioning systems. Viruses do not, however, grow or become more numerous inside of an air-conditioning system. They can grow or multiply only inside of living animal (and human) cells. This is why there is little discussion of viruses in conjunction with ventilating and air-conditioning systems.

Algae are plant like organisms that are sometimes associated with air-conditioning system contamination. They, however, require light in order to grow and prefer sunlight. Therefore, they are more of a problem outside and in such locations as cooling towers.

How They Grow

As you might have suspected, we are most concerned with fungi and bacteria because they grow rapidly in the dark confines of the interior of ventilating and air-conditioning systems. Actually, they prefer similar environmental conditions to those where we are most comfortable. Thus, when we create ideal living conditions for ourselves, those tiny pests thrive. Most prefer temperatures between freezing and about 120 degrees F. There are exceptions. Certain species grow at sub freezing temperatures and in extremely hot conditions. For the most part, however, most rapid growth takes place at ambient temperatures between 45-100 degrees F. Generally, the higher the humidity, the more rapid the growth and greater the survival rate of most species. Bacteria in fact often grow best in standing water (like in drain pans that don't drain). Fortunately, most fungi do not grow well unless humidity is above 65% or moisture is available on the surface where they are attempting to grow. Thus moisture control is the preferred way to limit fungal growth.

North vs. South

Unfortunately, surface growth has little to do with why such organisms are a problem. Surface growths are ugly and can damage the surfaces. When growth progresses far enough, the very mass of the accumulated growth can block airflow or cause other blockages. The real problem from the standpoint of indoor air quality is what gets into the air. This is the basis of the north vs. south debates.

When conditions are ideal for growth, colonies of organisms flourish. During this active growth, the organisms give off waste products. Some of these are gases that are released into the air. These gases may cause many of the problems we associate with so called "sick buildings". Investigators are still trying to determine what effect these gasses do have on human health if any. What is clear is that they stink. One of the least loved realities of the south for most of the year are the smells associated with the growth of fungi and bacteria.

A good thing about rapidly growing colonies is that they tend to stay put where they are growing. As humidity gets lower or moisture is no longer available, growth slows or stops completely. Organisms, however no longer stay in one place. As growth slows, fungi produce spores, which are like seeds that can form a new growth in the future. These are light and easily carried by air currents throughout a building. They are produced by the millions. In addition, dried portions of a colony can be eroded by an air stream and parts broken off and carried away from the growth site.

Both spores and fungal cellular matter contain substances that are toxic to humans and animals, trigger allergies and may impair the proper operation of the immune system. EPA has documented that airborne fungal matter dramatically increases as humidity falls from previously high levels. This fact may be responsible for the very high rate of colds, flu, and upper respiratory infections reported in the north. Many of these occur during a cold snap following a period of high humidity (and growth).

I'm still not sure which region of the country wins (or loses) the great debate. Is it better or worse to be sickened by foul smelling gasses than choked by airborne spores? What is clear is that by assuring good ventilating system hygiene, we can eliminate the growths that sicken our customers regardless of what part of the country we live in.

Mr. Baker's field of expertise is the control of contamination in air-conditioning and ventilating systems by mold, mildew and bacteria. He writes and speaks frequently about the efficacy, legal risks, and regulatory issues involved in various control strategies. He serves on ASHRAE Technical Committee TC 2.3, TC 2.4, TC 9.8, and Sampling of Airborne Particulate Concentration in Commercial and Residential Buildings GPC 17P. He also serves as a member of ASTM D22.06 (Indoor Air Quality) and is on the Board of Directors of the Indoor Air Quality Association and the Florida Public Health Foundation. Because HVAC applications encompass new uses from an U.S. EPA regulatory standpoint, Mr. Baker works closely with the EPA and industry groups, including serving as the chair of the IAQ committee of the Consumer Specialty Products Association, to help formulate policy in this area.

Bob Baker is Chairman and CEO of BBJ Environmental Solutions, Inc., a company specializing in providing clean air through environmentally responsible products, such as BBJ MicroBiocide , BBJ Micro Coil Clean , "FreshDuct Odor Eliminator ", and BBJ Mold and Mildew Remover™ as well as the revolutionary new Power Coil Clean™. For additional information, Mr. Baker can be reached at (800) 889-2251 or through the company web site at http://www.bbjenviro.com.