The cartridges are coded by what they protect against. That being said, the codes that are used really describe a larger group of chemicals by group. There is no chart available for what the designations mean online, but there is one in the Grainger catalog on the very first page of the respiratory section.
For this cartridge OV stands for organic vapors which is actually a general category for several different contaminants. Because there are so many organic vapors, it is broken down into a broader category. P100 is the new designation for HEPA and is meant for oil and non-oil particulates (the "P" in P100 means "oil-proof). It is 99.97% efficicent in filtering out particles that are .3 microns in size or larger.
If you have a specific question regarding which filter is best for your application, please contact your local Grainger branch and they can help assist you with cartridge selection.
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