Technical Analysis. Air Purification Technologies. Introduction. Common IAQ Pollutants and Their Sources. Particulates: VOCs and mvocs:

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1 Technical Analysis Air Purification Technologies Mark Misner CIE, CMI, CMRC Introduction Air purification is the process of removing airborne contaminates from the air. Common indoor air contaminates include Volatile Organic Compounds (VOCs), Microorganisms, Mold Spores, Particulates, and Allergens. In recent years, indoor air quality (IAQ) has become one of the leading health issues in the country. Both government and private research studies have linked many illnesses to poor IAQ. One of the fastest growing areas of medical diagnosis and treatment has become environmental and occupational medicine. Beyond allergies and respiratory tract infections, the consequence of poor indoor air quality includes asthma, hypersensitivity pneumonitis, lung disease and in extreme cases, cancer. According to the National Institute for Occupational Safety and Health (NIOSH) one-third of Americans are exposed to poor IAQ every day at home, office and schools. 1 In 2000 William Fisk, a noted indoor air quality researcher, estimated that the direct cost associated with allergies and asthma due to poor IAQ exceeds $15 billion annually. 2 In the same study, Fisk estimated the total medical treatment and lost productivity cost attributed to poor IAQ exceeds $60 billion annually. 3 As a result of the health and financial costs associated with poor IAQ, air purification technologies and new construction techniques are being aggressively developed and deployed to improve indoor environmental conditions. Unfortunately, many of the solutions being touted for improving air quality have limited or even negative consequences as well. Therefore, it is important to understand both the range of indoor air pollutants and the methods required to either limit or remove their presences in the built environment. Common IAQ Pollutants and Their Sources Particulates: Any small solid particle or liquid droplet suspended in the air are broadly referred to as particulates. These airborne pollutants include dust, smoke particles, dander, fibers, pollen, mold spores, bacteria, and viruses. If the particulate is biologic in nature (mold, pollen, dander, bacteria, or virus) it is referred to as a bioaerosol. The sources for indoor particulate contamination are many. Virtually all surfaces, materials, furnishings, and biologic matter can be a source of airborne particulates. VOCs and mvocs: VOCs and microbial Volatile Organic Compounds (mvocs )are a broad class of gasses that contribute to poor air quality. These chemicals include formaldehyde, hydrocarbons, vinyl chloride, methane, and chloroform. Common sources for VOCs include: paint, air fresheners, disinfectants, cleaning supplies, pesticides, building materials, furnishings, and sewage gas. In addition to chemical sources, microorganisms produce VOCs known as mvocs. These chemicals are outgassed as part of the metabolic process. mvocs include aldehydes, alcohols, and ketones. These are also the chemicals responsible for moldy, musty, earthy odors typically encountered in water damaged and mold contaminated buildings.

2 Ozone: Radon: Ozone is a naturally occurring form of oxygen consisting of three oxygen molecules. Ozone is considered an indoor air pollutant and at low parts per million (ppm) can cause headaches, nausea, and respiratory irritation. Even brief exposure of ozone at concentrations above 15 ppm can cause severe lung damage and concentrations above 50 ppm are considered lethal. Ozone is considered a leading cause for the trigger of asthma attacks and increases sensitivity to other indoor allergens like dust mites. 4 Both OSHA and the EPA have recently revised their permissible exposure limits (PEL) for indoor ozone levels to 0.1 ppm (time weighted average). Many researchers have been very vocal that these levels are still unsafe. Accordingly, California has banned the sale of any air purification device emitting more than 0.05 ppm ozone. 5 Radon is a colorless, odorless radioactive gas. While the number of deaths attributed to radon exposure is debated, the EPA states that radon exposure causes thousands of preventable lung cancer deaths every year. 6 Radon is a naturally occurring gas that is heavier than air. It seeps from the ground into crawlspaces, basements, and through foundation slabs. Even at low levels (4 picocuries per liter or less) radon has a negative impact on health. Structures built in defined radon zones must use either active or passive systems to mitigate the buildup of the gas. Asbestos: The use of asbestos in manufactured goods began to decline in the 1970's when it was shown that exposure to the fiber is linked to lung cancer. Once inhaled, asbestos causes lung damage resulting in lung cancer (mesothelioma). Therefore, in 1989, the EPA banned the use of asbestos in manufactured goods. The Centers for Disease Control and Prevention estimated that almost 1,500 die annually from complications resulting from asbestos exposure every year. 7 Common household materials that contain asbestos include, pipe insulation, shingles, linoleum flooring, drywall spackling, acoustic tiles and adhesives. Due to its prevalence in building and consumer goods, asbestos exposure is still a major concern today. IAQ Technologies In an effort to reverse poor IAQ, many technologies have been developed to remove or destroy airborne contaminates. Collectively, these devices are termed air purifiers ; however, their design and operation vary widely. While air purification devices may have a significant effect on one or more indoor air pollutants, no one technology has been able to address all IAQ issues. It is important to understand that certain IAQ problems cannot be addressed through air purification technologies alone. Radon, asbestos and mold contamination require special remediation procedures performed by certified specialists. Once the source of these contaminates has been removed, air purification technologies can be employed to maintain a healthy indoor environment. HEPA Filtration: High Efficiency Particulate Air (HEPA) filters are deigned to remove at least 99.97% of airborne particles as small as 0.3 micros. Typically, HEPA filters are constructed of layers of fiber mesh mats designed to allow air to pass through while trapping ultra fine particulates. HEPA rated filters capture mold spores, pollen, dust, as well as many airborne microbial pathogens. Most high efficiency air filters are disposable and therefore must be routinely inspected and replaced.

3 UV Lights: The germicidal properties of ultraviolet (UV) light was first discovered in the 1930's. Today, UV germicidal lights are sometime used in commercial and industrial applications to control microbial growth in HVAC systems. The effectiveness of UV light is a function of the intensity of the light source and the duration of exposure. Many organisms such as mold and algae require high intensity for long durations to be neutralized. In addition, UV lights can lose as much as 95% of their intensity within 12 inches from the emitter. Therefore, to be effective, sufficient intensity and duration must be calculated and properly maintained in order to be effective on static surfaces. High intensity UV emitters can cause surface damage to plastic surfaces and electrical wiring. Over time, this can damage equipment and lead to electrical arcing in wires. In addition, UV lights generate high levels ozone (0 3 ) during operation. In certain environments HVAC based UV emitters can exceed OSHA Permissible Exposure Limits for ozone exposure (0.1 ppm). Accordingly, the use of HVAC based UV germicidal lights has diminished since the 1990's. Ion Air Purifiers: Ion based air purification systems were a popular consumer item in the 1990s. The systems were designed to charge the air with positive ions and collect particulates on negatively charged collector plates. Through ionic attraction, aerosols were drawn to the collector plates and then removed through manual cleaning. However, one of the byproducts of ionization is ozone production. This lead the EPA to issue exposure warnings on ionic generators and many state agencies ultimately banned their sale. Ozone Generators: As discussed above, ozone is a highly reactive molecule that possesses very powerful antimicrobial performance. Ozone generators convert oxygen (O 2 ) to ozone (O 3 ) by charging the air through an electrostatic generator. This method of ozone production not only creates high concentrations of ozone, it also produces nitric acid and nitric oxides that are corrosive to metal surfaces. Accordingly, ozone treatment is only reserved for speciality disinfection applications. Moreover, ozone devices should not be used casually or in occupied buildings. Titanium Dioxide Photocatalytic Systems: Titanium Dioxide (TiO 2 ) systems also known as photocatalytic purifiers were first introduced in the late 1980's as a safe alternative to ozone generators. 8 TiO 2 systems convert ambient free water molecules into hydroxides (HO) and peroxides (H 2 O 2 ) through a photocatalytic reaction powered by UV light. Hydroxides and peroxides are highly reactive superoxide molecules that quickly oxidize VOCs and microbial/biologic contaminates. While hydroxide ions do not survive for more than a few thousandths of a second, peroxides are more stable and long lived. In sufficient quantity and duration peroxides will safely neutralize microorganisms. While the benefits of superoxides are well defined in controlled laboratory settings, TiO 2 systems have not lived up to the marketing claims made by some manufacturers. Sustained production of superoxides, catalyst bonding and UV emitter life has been a problem for TiO 2 systems.

4 Nano Alloy Photocatalytic Catalysts: Developed in 2007, nano-alloy catalysts (NAC) represent the second generation of photocatalytic superoxide generation technology. By replacing titanum dioxide with a more energetic catalyst, superoxide production is dramatically increased. Not only do NAC systems provide higher superoxide production, the bonded metal catalyst is far more durable than generation one TiO 2 systems. NAC photocatalytic systems provide measurable VOC, mvoc, and bioaerosol reduction without the release of ozone into the building. There have been several published articles demonstrating moderate to high reduction rates of microbial contaminants both inside HVAC systems and surfaces within the superoxide exposure zone. NAC photocatalytic systems provide the benefits of ozone generators and UV germicidal lights without occupant exposure hazards and surface damage. Today, second generation NAC systems are being utilized to control odors, VOCs, airborne contaminants, and pathogens in hospitals, nursing homes, schools and office buildings. Conclusion Natural air exchange and dilution of indoor air pollutants has been the traditional method used to control indoor air quality. Drafty homes and buildings did not harbor indoor odors and air pollutants. However, with the advent of energy efficient building designs, natural air exchange within buildings has been significantly reduced. In the residential building market, fresh air exchange has been almost completely removed. Accordingly, as energy efficient designs have proliferated and natural air exchange stopped, air quality within our structures has suffered. Microbial contamination, VOC buildup and occupant exposure has become a very significant public health concern. To ensure healthy indoor air, we must adopt new air quality measures and develop an integrated solution that embraced sound and safe purification technologies to improve indoor air quality. This solution includes particulate filtration, bioaerosol control, VOC reduction, ozone reduction, and pathogen reduction. This integration of technologies must be part of an overall indoor environmental plan. This plan should include the participation of HVAC engineers, IAQ investigators, Industrial Hygienists, and technology integrators. With the integration of new IAQ technologies designed to reduce particulates, VOCs, and microbial contaminates reversing poor indoor air quality is easily obtainable today. Furthermore, by harnessing the benefits of a comprehensive indoor environmental plan, building occupants can enjoy both energy efficient designs and a healthy indoor environment. 1 National Institute for Occupational Safety and Health Building Air Quality Action Plan 2 Fisk, William J Health and Productivity Gains from Better Indoor Environments 3 Fisk, William J Health and Productivity Gains from Better Indoor Environments 4 U.S. Environmental Protection Agency. Health Effects of Ozone in Patients with Asthma 5 California Environmental Protection Agency. Assembly Bill 2276 (2006, Pavley) 6 U.S. Environmental Protection Agency Assessment of Risks from Radon in Homes 7 Centers for Disease Control and Prevention Work-Related Lung Disease Surveillance Report 8 Maness PC, Bactericidal activity of photocatalytic reaction. Appl Environ Microbio. 1999;65(9):

5 Air Purification Comparison Chart Particulate VOC & mvoc Odor Ozone Bioaerosol Surface Disinfection HEPA Filtration Yes No No No Yes No UV Light No No No No - Generates 0 3 Yes Yes Ion Generator Yes Yes Yes No - Generates 0 3 Yes No Ozone Generator No Yes - Significant Yes - Significant No - Generates 0 3 Yes - Significant Yes TiO 2 Photocatalytic Yes - Limited Yes Yes Some Designs Yes Yes - Limited Nano Alloy Catalysts Yes - Limited Yes - Significant Yes - Significant Limited Yes - Significant Yes HEPA Filtration UV Lights Ion Generators Very effective at removing airborne particulates that circulate through the HVAC system. Has no effect on VOCs, odors, or ozone. Provides a bioaerosol reduction for many microorganisms outside of the HVAC system, but no surface disinfection effect. No particulate, VOC, or odor reduction. UV lights produce ozone therefore, air quality must be monitored if used. Surface disinfection can be achieved at high energy levels with sufficient duration. UV lights have only limited effect on bioaerosols within HVAC systems. UV radiation is harmful to many surfaces including plastics and electrical wire insulation. Systems are effective at reducing airborne particulates. Charged ions do provide a significant odor reduction effect. Some ion generators produce unacceptable levels of ozone. Ozone Generators No particulate reduction. Ozone is very effective against VOCs, odors, bioaerosols, and surface microbes. Because Ozone can be harmful and even lethal, it should only be used in unoccupied areas by competent remediation and disinfection professionals. TiO 2 Systems NAC Systems Standalone TiO 2 units reduce bioaerosols and odors within the immediate treatment area. Limited VOC reduction within the immediate are of the unit. Laboratory research has shown reduction of surface contaminates within confined treatment zones exposed to moderate levels of superoxides. Some units produce high levels of ozone and have been banned in California. Second Generation photocatalytic systems provide broader performance over first generation TiO 2 based systems. Because they are more energetic at low humidity levels, NAC systems are very effective in HVAC systems. NAC systems have shown significant VOC, bioaerosol, and moderate surface microbial reduction. Ozone production for NAS systems is less than.02 ppm.

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