There are three main rating systems: MERV, MRP and FPR. In all systems, higher ranked filters offer finer filtration and higher performance. The Home Depot uses the color-coded FPR system.
Finer filters are more effective at capturing impurities but reduce the energy efficiency of an HVAC system. It takes more power to pull air through a smaller mesh. Find the right balance for your facility to protect the air quality and energy costs.