When the entire spectrum of indoor air quality for commercial buildings is considered, a filter with an efficiency of MERV 13 or higher should be the product of choice. A MERV 13 filter will move the HVAC filtration system into the realm of controlling respirable-size particles, including most bacteria. Its higher efficiency will also address airborne mold spores.

MERV 13 filters with six air changes per hour would have "virtual 100% efficiency" in capturing most molds. It would also be highly effective on bacteria, since 98% of all bacteria known to man are over 1 micron in size and MERV 13 has an efficiency on 1-micron size particles of over 85 %.

In the past, air filtration systems in spaces such as offices and schools were designed primarily to protect HVAC equipment and reduce the need for facility cleaning. In recent years, people have become aware of the issue of indoor air quality as independent studies have focused attention on the toxic effects of airborne contaminants and the relationship of “sick building syndrome” to higher absenteeism and lower productivity. In turn, facility executives have felt increasing ethical, legal and marketing pressures to provide a high-quality indoor air environment for their occupants.

As society has begun focusing more on health issues, office buildings and schools have had to re-design the HVAC equipment built for commercial use. EPA and independent studies have shown that indoor air is 5 times, and sometimes even 100 times, higher in air borne dust, pollen, and mold spores. This has had an effect on the workplace. There is now “sick building syndrome” which correlates with higher absenteeism and lower productivity. Company executives have been pressured to consider ethical, legal, and marketing issues in providing clean air for their employees.

Air filtration systems aim to capture, in a cost-effective manner, as many of the suspended particulates, biological materials and gases from the air as possible. An air filtration strategy depends on the building’s occupancy, location, specific air quality issues, and the type and operation of the HVAC system. For example, the strategy for an airport terminal, which is subject to high volumes of diesel and jet fuel gases, differs from that of a typical office building.

MERV 13 filters or MERV 15 filters are effective for most commercial and institutional applications. Regardless of the efficiency of the filter, operating cost is quite specific to the building; there is no rule of thumb. This means the type of filter should be selected based on the specific building location, occupancy, air quality issues and type and operation of the HVAC system. However, it is reasonable to specify at least MERV 13 filters to maintain good indoor air quality in common types of spaces.