Years ago, I worked for a company that maintained indoor foliage. We were given literature that explained how NASA had done studies on how the plants cleaned the air. More recently, I came across an article about very small houses and air quality. In the comments, someone mentioned that certain plants give off oxygen during the day while others such as snake plants do it at night. That was new to me. Even more recently, I read an article that suggested putting a snake plant in the bedroom for better sleep. Okay, I'm convinced. I've taken the two little snake plants out of the kitchen window and placed them in the bedrooms.
Here is a link to a TED talk that describes how the concept of using plants to "grow air" was used in a building in Delhi.