There have been studies on indoor plants and air quality. The most well-known of which, I believe, was the NASA Clean Air Study [0]. The study suggested 1 plant

There have been studies on indoor plants and air quality. The most well-known of which, I believe, was the NASA Clean Air Study [0]. The study suggested 1 plant per 100 sq. ft. but a space station obviously isn't the same thing as a dwelling. [0]: https://en.wikipedia.org/wiki/NASA_Clean_Air_Study https://en.wikipedia.org/wiki/NASA_Clean_Air_Study