Plan Your Air Filtration Project Carefully
Improve your home air quality with an air filtration project. For example, several types of air cleaning devices remain available and each offers a design that helps remove certain types of pollutants.
Flat or Panel Air Filters
Flat or panel air filters typically maintain a MERV of 1 to 4. These filters are commonly used in residential furnaces and air conditioners. For the most part, these filters protect the HVAC equipment from the buildup of unwanted materials on the surfaces such as fan motors and heating or cooling coils, and not for direct indoor air quality reasons. They maintain low efficiency on smaller airborne particles and medium efficiency on larger particles.
Pleated or Extended Surface Filters
Pleated or extended surface filters maintain a MERV of 5 to 13. These filters remain reasonably efficient at removing small to large airborne particles. Filters with a MERV between 7 and 13 are likely to be nearly as effective as true HEPA filters at controlling most airborne indoor particles. These filters enable a quieter HVAC fan operation and higher airflow rates than HEPA filters since they maintain less airflow resistance. Higher efficiency filters with a MERV of 14 to 16 are similar in appearance to true HEPA filters.
High Efficiency Particulate Air (HEPA) Filters
High Efficiency Particulate Air (HEPA) Filters have MERV values of 17 to 20. True HEPA filters are normally not installed in residential HVAC systems. True HEPA filters in an existing HVAC system would likely require professional modification of the system due to their physical dimensions and increase in airflow resistance.
Gas-phase Air Cleaners
Gas-phase air cleaners remove gases and odors by using a material called a sorbent, such as activated carbon, which adsorbs the pollutants. These filters are typically intended to remove one or more gaseous pollutants from the airstream that passes through them. Because gas-phase filters are specific to one or a limited number of gaseous pollutants, they will not reduce concentrations of pollutants for which they were not designed.
UVGI cleaners (ultraviolet germicidal irradiation) use ultraviolet radiation from UV lamps that destroy biological pollutants such as viruses, bacteria, allergens and molds that are airborne or growing on HVAC surfaces (e.g., found on cooling coils, drain pans, or ductwork). If used, UVGI cleaners should be applied with, but not as a replacement for, filtration systems.
PCO cleaners (photocatalytic oxidation) use a UV lamp along with a substance, called a catalyst, that reacts with the light. They destroy gaseous pollutants by converting them into harmless products. Just as with UVGI cleaners, PCI cleaners should be applied with, but not as a replacement for, filtration systems.
Portable Air Cleaners
Portable air cleaners generally contain a fan that circulates the air in conjunction with one or more of the air cleaning devices discussed above. These cleaners work throughout a home by moving from room to room and used when continuous and localized air cleaning is needed. They may be an option if a home is not equipped with a central HVAC system or forced air heating system.
Portable air cleaners can be evaluated by their effectiveness in reducing airborne pollutants. This effectiveness is measured by the Clean Air Delivery Rate, or CADR. The CADR is a measure of a portable air cleaner’s delivery of contaminant-free air, expressed in cubic feet per minute. For example, if an air cleaner has a CADR of 250 for dust particles, it may reduce dust particle levels to the same concentration as would be achieved by adding 250 cubic feet of clean air each minute. While a portable air cleaner may not achieve its rated CADR under all circumstances, the CADR value does allow comparison across different portable air cleaners.
Many of the portable air cleaners tested have moderate to large CADR ratings for small particles. However, for typical room sizes, most portable air cleaners currently on the market do not have high enough CADR values to effectively remove large particles such as pollen, dust mite and cockroach allergens.
Air cleaning devices can help to control the levels of airborne allergens and particles in a home. They can help reduce the levels of dust, pollen, dust mite and cockroach allergens, some molds, gases, odors and animal dander. Different types of filters work best on different airborne contaminants. An experienced contractor can help you select which type of system is best for your home.