What was the filtration level of the filter system? What was the orientation/positioning? I’m wondering if the airflow was in a loop but not mixing the entire

What was the filtration level of the filter system? What was the orientation/positioning? I’m wondering if the airflow was in a loop but not mixing the entire room, or the filter wasn’t Hepa (or close), or it wasn’t reaching its claimed throughput/filtration, etc. I recently installed a Merv13+Merv16 filter on my newly upgraded HVAC system and am able to drive PM2.5 to 0 with a minimal fan setting of roughly 2ACH. (Granted, we haven’t had wildfire smoke that strongly since installing it, but I induce bad air from time to time and it cleans it up quickly.)