Hey guys.....new to the site. I am a Safety Supervisor for a large Maintenance Org. I would suggest looking into the MSDS. My groups are wearing the 3M 7500 series. 85% of people wear the 7502 (medium). We have went this style because of the modular construction for cleaning and better seal with new material. I Fit Test our employees and the most important concern is a tight comfortable seal. The P-100 filter is the most common filter but we work out of 83 different factories currently and conditions on MSDS dictates the filter based on work task.......Always be safe and research the MSDS for recommendations. Go with Half-Mask vs. the paper 85N or 95P.