By Bob Baker

In the previous issue, we discussed techniques to control microbial contamination in HVAC systems. We mentioned in passing that you should not use "hospital type" disinfectants in HVAC systems. Additionally, we went into some detail about the health care role of these disinfectants and how that is different from the needs in the air-conditioning system. We repeated our warning that antimicrobial agents (including Hospital Disinfectants) should not be used in air-conditioning systems unless the Environmental Protection Agency (EPA) has specifically registered them for those applications.

This issue, we want to turn around to the positive and explore the question: What role do disinfectants have in improving indoor air quality? Actually, for the professional who understands these products and their proper use, there are potentially important applications.

Disinfectants can improve IAQ

When we addressed infection control, we concentrated on hospitals and other health care facilities. Infection control, however, is becoming an important need in both homes and all types of commercial facilities. Where people gather, whether for work or play, they bring large quantities of bacteria and fungi and some of these organisms are pathogenic (or disease causing). As we hear more about the dangers posed by Legionella, tuberculous, and the many deadly viruses that have become common in recent years, we all become more interested in having clean, germ free environments. As a result, the use of disinfectants is increasing rapidly.

From an indoor air quality standpoint, reducing the overall level of germs in a facility (known as bioburden) also lowers the number carried into the air stream of that facility. Conversely, the use of the wrong disinfectant or the improper use of a disinfectant, can be an air contaminate. As you can see, disinfectant usage is a double edged sword from an IAQ perspective.

Another Tool for Professionals

Although only EPA registered air-conditioning sanitizers should be used in the HVAC system, disinfectants, when properly used, can reinforce the activity of the sanitizer and serve as an invaluable tool. This is especially true of the so-called disinfectant/cleaners that combine the germ killing ability of a disinfectant with a cleaning agent. These save considerable labor as they can do two jobs at once.

There are some important jobs for the technician that involve both cleaning and germ killing. HVAC system components contaminated with dirt and microorganisms must be cleaned as part of a complete job. Grills, vents and diffusers removed to gain access to the duct interiors, as well as other components depending on the design of the system, require a thorough cleaning before reinstallation. Much of the soil, however, is mold and bacteria that must also be treated with an antimicrobial to prevent the possibility of regrowth. Technicians should sanitize these before reinstallation.

Many technicians like to use a disinfectant to "knock down" the level of contamination in parts of the equipment before starting their work. They prefer a disinfectant to a sanitizer because the action is more rapid and they can proceed at once to clean. Since this results in the components being completely cleaned and provided the disinfectant is rinsed off, this practice is acceptable and will not cause contamination of the air stream. Components inside the air handler and air ducts treated with a disinfectant/cleaner should always be rinsed off to prevent hazardous fumes from entering the air stream. This may not be the case, however, for sanitizing agents that are specifically registered for use in HVAC systems. The manufacturer's instructions should be followed regarding application and rinsing.

Additionally, use of a disinfectant/cleaner will assure that contamination is not moved from job to job. A handy spray bottle can be used to spray down tools, shoes, glove and other items that might spread contamination.

From time to time, technicians face microbial contamination that is outside the system. This can vary from some minor mold streaks on the wall or ceiling near vents to whole surface areas that are green or black with growth. This microbial growth must be removed. This is because it detracts from the appearance of the facility and its presence poses a high risk of re-contamination in the near future. A disinfectant/cleaner is ideal to remove this contamination. For minor contamination, the technician may wish to remove it as part of the service. In more involved cases, you should either explain to the customer the importance of having the area cleaned with a disinfectant or contract for that service as an extra.

Finally, as we have pointed out previously, carpeting and upholstery contain dust and other particulates that support high levels of microbial growth. When not properly maintained, these fabric surfaces can contribute major microbial contamination to the facility. Each time someone sits on a contaminated chair or sofa or walks on a contaminated carpet, thousands of dust particles carrying viable organisms are puffed into the air. They can have a strong impact on the comfort and welfare of those in the facility. When they are carried back through the HVAC system, they constitute an added cleaning burden on the filtration section of the system. Those dust particles that bypass the filters will begin the cycle of contamination in the system all over. Thus, an excellent system cleaning and decontamination job can be quickly recontaminated from a source outside the system. Even if a service professional is not in the business of cleaning upholstery and carpets, it is in his or her interest to see that those items are properly maintained using the proper disinfectant/cleaner.

Clearly a disinfectant/cleaner is an important tool of the indoor air quality professional. It can be used to:

• Clean and disinfect grills and vents.
• Disinfect tools to prevent contamination spread.
• Knock down extreme contamination to increase worker safety.
• Remove and inhibit regrowth of unsightly exterior surface growth.
• Prevent fabrics from becoming a source of re-contamination.
• Reduce overall facility bioburden.

You will recall, that we emphasized that using the wrong formulation or improper use can result in the disinfectant becoming a source of air contamination. In the next issue we will review the various types of disinfectant formulations on the market and explore their nature and potential for releasing contamination into the air.

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.