When it comes to air filtration, MERV 13 filters are often considered the gold standard. But is this really the best choice for your home? To answer this question, it's important to understand what MERV ratings are and how they work. MERV stands for Minimum Efficiency Reporting Value. It's a rating system used to measure the effectiveness of air filters in capturing particles of different sizes.
The higher the MERV rating, the more efficient the filter is at capturing particles. Filters with MERV-13 ratings or higher can capture particles as small as 0.3 microns in size. This means that they can effectively remove dust, pollen, mold spores, and other airborne contaminants from your home. However, if chemical disinfectants are used, they should only be applied with the HVAC system turned off.
In addition, disinfectants should not be applied to ventilation filters before continuing to use the filters within ventilation systems, as the effects of disinfectants on filter performance are unknown. Filters should only be treated with disinfectants if they are to be removed from service and disposed of. While UV systems are quite effective at maintaining the cleanliness of HVAC coils, drain pans, and other damp surfaces, properly designed systems can be quite effective in inactivating microorganisms in moving air streams on the fly. These systems generally require more lamps, so they can provide significant UV doses in a short period of time.
A typical one-pass inactivation efficiency is 85%, just like a good particulate filter, but systems can also be designed for inactivation greater than 99.9%. In addition, a well-designed UV air disinfection system within an HVAC system, and located adjacent to the cooling coils, can also provide the surface disinfection benefits mentioned above. Another way to install UV is in a “top air” configuration. Specially designed wall-mounted fixtures create an irradiated area above the occupant and disinfect the air in the space, as the air circulates naturally, mechanically or through the HVAC system.
CDC has approved this type of system for use in tuberculosis control for nearly 20 years, and there is guidance from NIOSH on how to design them. Finally, mobile UV systems are frequently used for terminal cleaning and surface disinfection in healthcare facilities and other spaces. Systems such as these are commonly used in unoccupied spaces due to occupant exposure concerns. The three types of systems can be relevant, depending on the type of building and the individual spaces within the building. The design and sizing of effective ultraviolet disinfection systems can be a complex process due to the need to determine the dose delivered to a moving air stream or to an irradiated region of a room. In-duct systems are further complicated by the configuration of the air handling unit and ducts and surface reflections that can help achieve higher irradiation levels.
Overhead air systems require proper air mixing to function properly while paying close attention to reflective surfaces that could cause room occupants to be overexposed to UV energy. Accredited manufacturers and system designers can help by making the necessary calculations and designing specific systems for individual spaces. MERV 16 is the tallest filter you can buy, but your air conditioning system may not be able to handle it. The reason the pressure drop is so low for a fiberglass filter is because it is extremely porous and, as a result, ineffective at filtering. This means that 81.5% of the dust particles introduced into the filter were successfully filtered out of the air. MERV ratings determine the capabilities of an air filter and its level of filtration efficiency.
Any air filter rated higher than 13 will restrict airflow to the point that it could damage your HVAC system, creating an additional expense to repair it. For HVAC systems, ASHRAE recommends a filter with a minimum MERV rating of 13, but MERV 14 or higher is preferred. For the European standard, a True HEPA filter will filter the air and capture at least 99.95% of 0.3 micron sized particles. MERV 13 air filters will provide the cleanest air quality in your home, acquired through the use of an air filter. The worst percentage of the six tests is selected as the official measure used to determine the MERV rating of a filter. Because HEPA filters are so efficient, they cause a greater pressure drop than MERV-rated filters.
Even though pleated filters have a slightly larger initial pressure drop, it's not significant enough to cause any damage to your HVAC system, as long as you change filters regularly. A HEPA filter is essentially the ultimate solution in the air filter world and far exceeds what a MERV 13 can do. MERV 14 and higher can capture particles that are even smaller than previous MERV ratings, ranging from 0.3 to 1.0 microns in size. So when it comes down to it, MERV 13 filters are an excellent choice for most homes when it comes to providing clean air quality without damaging your HVAC system.