Protection from Wildfire Smoke

My son has asthma and the wildfire smoke has been making him cough.  It is a nasty, goopy cough, which has garnered some fun stares in COVID times.  His asthma specialist recommended that we purchase HEPA air purifiers and place them in our home.  This is also the best way to deal with wildfire smoke even if you do not have asthma.  However, if you do not want to go out and buy expensive HEPA filters, check out this great video from the University of Michigan on how to make a HEPA air purifier yourself! https://www.youtube.com/watch?v=kH5APw_SLUU