Bryan Cumming and Michael Waring crunched the numbers to find out, if a person wanted to use houseplants to improve air quality in their home, how many plants they would need for effective air purification. In Cumming and Waring’s report, titled “Potted Plants Do Not Improve Indoor Air Quality: A Review and Analysis of Reported VOC Removal Efficiencies” in the Journal of Exposure Science and Environmental Epidemiology, the authors provide a clear-cut answer. A home with 1500 square feet of space would require 680 plants to be growing inside in order for the plants to effectively purify the air.