For non-powered particulate filters, which letter represents the most resistance to oil degradation?

Non-powered particulate filters are classified by NIOSH with letters indicating oil resistance: N (not resistant to oil), R (resistant to oil), and P (oil-proof, most resistant to oil degradation). TheGeneral Pest Management: Guide for Commercial Applicators - Category 7A(Chapter 3: Pesticide Safety) explains that P filters offer the highest resistance to oil degradation, making them suitable for environments where oil-based aerosols may be present. Option A (N) offers no oil resistance, and Option C (R) offers moderate resistance but not as much as P.