MERV 11 filters are an effective solution for controlling dust, pollen, mites, and pet dander in commercial buildings, residences, industrial workplaces, and paint booths. However, when using these filters in an industrial setting, there are some special considerations to keep in mind. If chemical disinfectants are used, they should only be applied with the air conditioning system turned off. Additionally, disinfectants should not be applied to ventilation filters before continuing to use them within ventilation systems.
The effects of disinfectants on filter performance are unknown, so they should only be treated with disinfectants if they are going to be removed from service and discarded. Ultraviolet (UV) systems are highly effective at maintaining the cleanliness of HVAC coils, drain trays, and other damp surfaces. Properly designed systems can provide significant doses of UV in a short period of time and achieve a single-pass inactivation efficiency of 85%, which is comparable to that of a good particulate filter. Systems can also be designed for inactivation greater than 99.9%.
In addition to providing surface disinfecting benefits, UV air disinfection systems can also be installed in an “aerial” configuration. Wall-mounted accessories 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. The Centers for Disease Control and Prevention (CDC) has approved this type of system for use in TB control for nearly 20 years, and there is guidance from the National Institute for Occupational Safety and Health (NIOSH) on how to design them. Mobile UV systems are also frequently used for cleaning terminals and disinfecting surfaces in health centers and other spaces. Designing and sizing effective ultraviolet disinfection systems can be a complex process due to the need to determine the dose administered to a moving air stream or to an irradiated region of a room.
Inlet systems are further complicated by the configuration of the air handling unit and ducts and reflections from surfaces, which can help achieve higher irradiance levels. Superior air systems require an adequate air mix 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. A MERV-11 filter will eventually achieve HEPA-level filtration as the trapped particles (filter bed) become established over time. It is important to note that high MERV filters can reduce the lifespan of HVAC equipment, damage equipment, reduce air flow, and increase operating costs.
Therefore, it is important to consider the location of the filter on the grid and whether a larger filter is necessary. The most commonly used filters are those in the MERV 13 to 16 range, which capture lead, humidifier dust, nebulizer dust, carbon dust, legionella bacteria, insecticide dust and copier toner particles, sneeze nuclei particles, car fumes particles, and bacteria particles. These filters are especially important when dealing with wildfire smoke or COVID-19 virus particles. Finally, it is important to clean return ducts periodically as dirt can accumulate before reaching the filter. This will help ensure that two filters with the same surface area and micron size will have the same airflow.
