As Allison Bailes writes in his most recent Energy Vanguard post, filtration is on the minds of a lot of people lately: 

"Because of the coronavirus pandemic, most of us would prefer not to breathe in air that contains any hint of the SARS-COV-2 virus that's been spreading the illness known as COVID-19.  Wearing a mask when going out in public is standard.  Having clean air at home is good, too, and good filtration in your home's HVAC system can help, too.  I had the HVAC  system replaced at my home last November and recently spilled the beans about how I undersized the new Mitsubishi ducted mini-split heat pump."

In this post, Bailes reports on how he sized his system's air returns, and takes a deeper dive into the filters that he uses to clean the air that flows through his ductwork.
Read more.