Certified GKH Gardening Expert
This depends on the type of plant. If you are referring to the capability of filtering air, then this heavily depends on the plants capacity to do so. Somewhere around 25 house plants will filter a small house, but there could be more or less depending on the plant's ability to clean air.
Here is an article with more information: https://www.gardeningknowhow.com/houseplants/hpgen/growing-houseplants-in-bedrooms.htm
Thanks Bush Dr.
But I wanted to get more info because I am trying to present a project at the place I work at (office) and explain or suggest how many plants we should get... the office area is aprox 35,000 sqft and we have about 280 ppl.