Another random google link says it could be as little as four shoulder-height areca palms: http://www.secrets-of-longevity-in-humans.com/oxygen-producing-plants

Another random google link says it could be as little as four shoulder-height areca palms: http://www.secrets-of-longevity-in-humans.com/oxygen-producing-plants.html http://www.secrets-of-longevity-in-humans.com/oxygen-produci...