Dr. Jeffrey E. Terrell, director of the Michigan Sinus Center, demonstrates how to build an air purifier with a HEPA filter for about $25 with parts from your local hardware store.
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Build a do-it-yourself air purifier for about $25
Dr. Jeffrey E. Terrell, director of the Michigan Sinus Center, demonstrates how to build an air purifier with a HEPA filter for about $25 with parts from your local hardware store.
source