The first step in filter selection is to determine what the objective is for the filtration system. What is the ‘target’ particle size for the application? As an example the ‘target’ particle size in most health care facilities is one micron because 99% of all known bacteria are one micron and larger. The filter guide figure below might offer some assistance as it shows the typical distribution of particles in ambient air. Once the objective has been determined Table 12-1 (below) will be useful in determining which MERV efficiency will remove the target size particles. More detailed efficiency numbers can be found in the ASHRAE 52.2 Test Report.

Once the target MERV rating has been established Table E-1 on the first page converts the MERV ratings into the various filter options offered by Tri-Dim. Filters with a MERV 13 and higher typically utilize a prefilter to maximize their service life and minimize their life cycle cost. Tri-Dim can help in the process of filter selection by having one of our factory trained sales representatives assist in the process of identifying the ‘target’ particle size and then develop those identified objectives into a filtration protocol. Tri-Dim offers this technical service free of charge.