• HEPA (High Efficiency Particle Arresting) filtration is the most widely known method for purifying air. It can be found on the shelves of every local drug store, hardware store, and general merchandiser for as little as twenty dollars and as much as several hundred. Many HEPA products make the claim that they clean 99.99% of particulate in the air. This is true depending on the micron spec for the filter but the air has to be drawn through the filter. To properly clean air through filtration there must be a complete air exchange of four times in an hour. To achieve this in a normal size room requires a fan with high a CFM rating. HEPA systems are not always efficient at drawing the amount of air needed through the filters and they do nothing to the source of mold, mildew, bacteria, and other fungi. In some cases HEPA filters become a breading ground for many fungi.
   
• Electrostatic Filtration is a filter with a negative DC charge to attract particulate. In comparison to most HEPA systems it is more effective in trapping smaller micron particulate and effective in clearing smoke from the air. It will reduce odors but it will not eliminate them. Electrostatic filters are able to neutralize most mold, mildew, bacteria, and other fungi that comes in contact with the filter. This technology has to draw air through it to be effective and it does little to the source of the fungi. This technology usually requires a fan with high CFM and has filters that have to be cleaned.
   
• Ionization also uses a negative DC charge to produce an abundance of negative ions. Most ionizers are effective in settling dust and particulate out of our breathing space. One must be careful in evaluating some of these products as there are questions about whether they can actually do all that are claimed. For example, Ion generators work great for the room that they are in, but there is no scientific evidence that they will project through walls or ceilings as some products claim. The production of negative ions indoors helps create a natural balance that is lost with our tightly sealed buildings and homes.
   
• Ozone via corona production. Corona technology was popular in the 80's and early 90's. It is produced by applying a high voltage to conductive materials separated by a dielectric which excites the oxygen molecule to create Ozone (O3). Ozone is a very powerful oxidizer that will neutralize odors, mold, mildew, bacteria, and other fungi. This technology is commonly used in flood and fire restoration. The amount of O3 produced in occupied spaces is regulated by the EPA and FDA among others. The standard for ozone states that it must remain below .05ppm indoors. When sending a high voltage across a dielectric to produce O3 there is also the production of Oxides of Nitrogen. This is because of the high nitrogen content in our atmosphere. Oxides of Nitrogen are found to be offensive in odor, corrosive which can adversely affect components, and can cause side effects such as headaches and nausea. Ozone is found to be effective because it works on the problem at the source and air does not have to be pulled through the unit for treatment
   
• UV Germicidal Lamps are commonly used for disinfecting purposes. UV lamps can be found in hospitals and several grocery store chains for sanitation reasons. This technology is effective in sterilizing air and surfaces that come in contact with the UV light. In more recent years technology has been developed that produces Ozone in combination with a UV bulb. This method is found to be a way of producing cleaner Ozone without the production of Oxides of Nitrogen. Lamps generally have to be replaced once a year.
   
• Photocatalysis uses light which reacts with a catalyst resulting in oxidation. This is found to be effective in destroying mold, mildew, bacteria, other fungi, dust mites, and many odors. This technology is produced with an Ozone/UV lamp set in a variety of combinations. The lamp is in direct visual contact with metallic targets. Titanium Dioxide (TiO2) is commonly used because it will react with UV alone. New research is establishing that when used in combination with other metals such as Zinc and Copper its effectiveness is multiplied many times. When this type of photocatalysis is combined with the natural humidity in indoor air it creates hydroxyl radicals and super oxide ions that are effective in combating fungi. This method is also a pro active approach that goes to the source for treatment. This technology generally requires the lamp and targets to be replaced once a year.

In conclusion, when doing your research, use this as a guide for asking questions of the manufacturer of any product you're evaluating. Indoor air pollution is a problem that is not going away any time soon. As we learn more we are discovering more about the negative effects it has on your health. Your customers are already concerned about their health and the safety of their families. They will appreciate you taking the time to become familiar with what is available to help them. The air treatment industry is dynamic and new and better ways of dealing with the problem are being discovered all the time.

-- Water Technology Magazine, May Issue