What the the effects of houseplants?
There are also many claimed psychological and physiological benefits to having houseplants. Houseplants do have a statistically significant effect on the concentrations of both carbon monoxide and carbon dioxide in normal indoor environments. 
Plants also appear to increase the number and diversity of bacteria in homes, while reducing fungal diversity.They tend to increase humidity, reduce temperature swings, and reduce noise. There are also many claimed psychological and physiological benefits to having houseplants. Indoor plants can provide psychological benefits such as stress-reduction and increased pain tolerance.