The difference is moot; those 1989 experiments have long since been shown to have little application in everyday conditions in typical buildings. The experiments were conducted in small, sealed environments, not a house. It's since been proven that simply opening a window is more effective at purifying indoor air than installing houseplants. Doesn't mean that having indoor plants isn't good for your mental health; just don't count on them to benefit your lungs.
It's amazing how persistent and maleable some stories are. Not only won't this one go away, alleged air purification claims keep growing and spreading. The number of articles in a single Google search is astonishing.
https://www.lung.org/blog/do-h....
https://en.m.wikipedia.org/wik...
https://apnews.com/article/fac...
