Today’s Filtration Requirements
Since the Covid-19 pandemic began many commercial buildings have resolved to increase the MERV rating on the building system filtration. The standard MERV-8 rating filter used in the past is no longer meeting the building requirements to help prevent the airborne transmission of viruses and bacteria’s.
Since the pandemic began many of the recommended HVAC strategies have revolved around three avenues which has been to increase ventilation, increase filter efficiency and ultraviolet energy, often in a layered approach.
To help prevent the airborne transmission of the virus the ASHRAE guidance is to upgrade your HVAC filters to at least a MERV-13 rations. However, HVAC manufacturers and facility engineers are quick to caution that not HVAC systems, particularly aging systems, can handle the high airflow restrictions and stat pressure of the MERV-13 filters. Fortunately there is an easy-to-implement alternative for the HVAC systems that were never intended to perform with MERV-13 (and higher) filters.
Through a hybrid approach a facility can combine medium efficiency filters (MERV-8) with ultraviolet germicidal components or shortwave energy in the ultraviolet-C spectrum to yield near MERV-13 level efficiency rates without sacrificing air-flow or compromising cooling capacity.
Besides source control and increase ventilation, this layered approach has been shown to complement filter operation and increase longevity of filter life. For example, marrying UV-C air purifiers with filtration can increase the overall system’s pathogen removal rate since the MERV-8 filters captures the larger pathogens and air purifiers inactivate the smaller more susceptible pathogens.
For example, fungal and bacterial spores, which are less susceptible to the air purifiers are typically large (1-10 microns or more) and are more easily removed by a MERV-8 filters. But viruses and bacteria which are smaller (0.1 to 1.0 microns) can penetrate filters but are highly susceptible to the air purifiers. Therefore, combining filtration and air purifiers offers an ideal situation to address the full complement of microorganisms found in most indoor environments. Use of this two tiered system has been shown to significantly reduce respiratory symptoms in office buildings and to lower contact infections by as much as 40%.