Ductwork in commercial and residential forced air heating and air conditioning systems circulate air throughout your building in the process of heating and cooling. Any biological pollutants, contaminants, pathogens, bacteria, microbes and viruses present in the air circulating around the HVAC system are breathed in and also settle on surfaces in all the rooms. Exasperating this problem in newer buildings is the fact that most are constructed to be more sealed or tighter for energy efficiency which in turn reduces fresh air exchange or ventilation. The same pollutants and disease causing organisms become concentrated and readily multiply. Also typically air duct work is a friendly, hospitable place for fungi, bacteria and mold to grow and spread. Like most living organisms, they require temperatures between 40-120 degrees F, food and moisture, conditions which are present in commercial and residential heating and A/C duct work. This can result in poor IAQ or indoor air quality, some times referred to as sick building syndrome, not only having possibility of making us sick but understandably promoting allergic reactions and exasperating asthma conditions.
To reduce our exposure to such biological pollutants and contaminants at home, at work and in public places, we need to attack this increasing problem on several fronts. Increasing or providing adequate fresh air ventilation can help reduce the concentration and trapping of these bacteria and pollutants. Reducing humidity or moisture levels to less than 50% or even 30% will help prevent condensation and disrupt growth of microbes, bacteria and mold. Of course reducing the sources of biological pollutants and even destroying or eliminating those present is paramount. Methods tried to reduce and eliminate circulating biological pollutants include cleaning of air ducts and decontamination of air ducts using chemicals, biocides, fungicides and ozone. Unfortunately duct work cleaning has not been proven to be effective. The EPA (Environmental Protection Agency) in fact not only has stated that air duct cleaning has never been shown to actually prevent health problems but EPA also does not recommend that air ducts be cleaned except on a as needed basis. Regarding decontaminating heating and A/C systems including duct work, the EPA has stated that there is an unresolved controversy over the necessity and wisdom of introducing chemical biocides and ozone into duct work. The American Conference of Governmental Industrial Hygienists made an even stronger statement saying that application of chemical biocides as opposed to removing microbial growth and settled biological material is considered unacceptable. Still the fact remains that unhealthy biological pollutants and microbial growth are circulating around and residing in our duct work and it is imperative that something be done to reduce and eliminate it.
Beyond increasing fresh air ventilation and reducing moisture or humidity levels to help control biological pollutants and growth, there is considerable growing interest in deploying copper material for use as duct work. Copper has already been well documented and proven to destroy harmful bacteria, germs, microbes, pathogens, molds, fungi and viruses which come in contact with copper surfaces. Copper is also EPA approved as an antimicrobial agent after exhaustive tests confirmed it's effectiveness. Plus copper is inherently much safer than widespread use of ozone and chemical biocides - germicides whether liquids, sprays or aerosols. Copper and strong copper alloy materials are already proving effective in reducing the existence of biological pollutants, biological growths and bioaerosol contaminants in A/C duct work. Copper is quite an order of magnitude better than materials historically and commonly used for duct work such as galvanized steel, aluminum and stainless steel. While copper will not cure all IAQ problems and continuing studies will quantify it's measurable improvement in indoor air quality, it is known that usage of copper duct work will improve IAQ and is a positive step in the right direction. While we are waiting on definitive EPA approval for performance and health claims of copper duct work, builders and remodelers might also consider copper for it's elegance, beauty, richness, longevity, durability and corrosion resistance which are all much greater than any other material. Not coincidentally, these are the same reasons we have seen copper's ageless popularity for use in building architectural features and also increasingly in copper kitchens and copper home decor.
Copper Duct Work photos courtesy of Revere Copper Products