Up in Lake County we are getting smacked pretty hard with the Canadian fires smoke. It hits my mom in her 90's with breathing issues like a ton of bricks. I am keeping her inside as much as possible. My furnace filter is 5 inches thick, blower runs 24/7. I have been using 3m rated at 12merv but have just installed a Lennox rated at 16merv. I have 2 portable filter units in the house running on Medium with fresh filters. What else can I be doing? Do all these filters even help with indoor air quality?