Do they make you happier? Calmer? Less stressed? More productive? Quicker to recover from illness/surgery?
A pretty strong YES to all of those! And research on that is abundant (McGill review).
But do they purify the air in your house?
I know you've probably heard this claim a lot, and it's a very seductive thought, partly because it seems so reasonable: plants create oxygen, plants can absorb toxins according to that one 1989 NASA study, and I love having them in my house - surely they have this amazing functionality as well?
Fig.1 - Face planter at The Leaf House. (For ordering click here.)
And yes, it's a fact that plants can absorb toxic elements such as benzene, formaldehyde, and trichloroethylene (TCE) from the air around them.
And they do a dang good job of it too, over 24 hours -- if your space is the size of a car trunk.
Yep. The containers used in the NASA experiment to test each plant were 30x30x30 *inches* - that's about two and a half feet each side.
Extrapolating that to your room: you'd need about 50 snake plants in a smallish bedroom (10x10 feet) to even start making a difference to the air quality in there!
Just some of the snake plants you'd need in one room to purify the air in it.
And that's with keeping the doors and windows closed for 24 hours, shining bright lights on the plants, and keeping the room at a comfortable temperature.
Not to mention the air turnover that happens in rooms/houses on an hourly basis, nullifying any "purifying" effect your indoor plants might have had on the air in any case.
Which all is not to say don't get plants for your indoor spaces!
Plants in your bedroom, living room, office desk, workspace, study - wherever you spend any time at all - do have many well-documented and positive effects on mood and health. Plants are amazing and easy indoor companions, why deny yourself the joy and pleasure of their fresh leafy company?