About a year or more ago, I was breezing through Youtube and ran across a video from Michigan University where it was demonstrated an effective way to remove certain particles from the air. It was shown that this simple DIY air cleaning system was almost as good as the $800.00 and up air cleaning systems one could purchase. I already had what I needed at home which was a cheap box-fan that of 20 inch on each side. (A standard size). I paid about 16.00 for it at walmart. What I didn't have was an furnace air filter. I started reading about furnace air filters and how good they are and to what extent they filter specific particles out of the air. Merc is the measurement used. THe higher the Merc number, the more a filter is able to remove smaller particles. Knowing that virus particles are < 0.3 I chose the Filtrate Merc 13. A tad expensive for me for summer, spring and fall. However, since I am inside a lot in the cold months I used the Merc13 during the early days of the pandemic and winter months. Normally I purchase Merc 11. Overall the outside Furnace filter size should be the same size as the fan that you use. So I purchased a 20 inch by 1 inch furnace filter. Looking at the arrow on every filter, will show which way the air should be flowing through the filter and attached fan. I placed the filter on the Back of my box-fan with painters tape. I taped it so that no air could seep around the filter. I securely taped the the square cardboard filter to the back of my box-fan. After seeing no gaps between the metal fan grill frame and the cardboard filter frame, I plugged it in. Voila! It didn't take long to collect the long dog hair coming from carpet and air. It also didn't take long to see dirt stick to the box fan. I was shocked! After a few hours, I moved the fan to another room. I got the same result. After the very first week, I replaced my filter. After that, I found the filtering was working and not as much hair, dirt and "unseen" particles were building up on that filter. After my initial week, I am able to change the filter only once a month. Merc 13 filters and higher numbered Merc measurements are the only filters that catch particles as small as virus particles. (even virus particles caught will be on dust or hair or water droplets) Virus particles alone are nearly impossible with a furnace filter. I purchased the Filtrete dark colored Merc 13 in winter-time and during heavy pollen/allergy times. Other times of the year I use the lower numbered Merc 11 filters. (11's are good medium filters, for dust, hair and man chemicals). There is quite a difference in costs in which Merc filters one purchases. I live in a 1 bedroom ground floor apt. I highly suggest using this DIY filter while sleeping (for dust mites and dust). These filters are very good as well as for areas subject to molds or damp areas. Below is a video showing you how to put this DIY air cleaner together. Enjoy! You can do this.

https://www.youtube.com/watch?v=9XdYoI1awlU