Kamal Meattle's primary result was demonstrating increased blood oxygen levels in occupants of buildings with large numbers of plants. This is consistent with

Kamal Meattle's primary result was demonstrating increased blood oxygen levels in occupants of buildings with large numbers of plants. This is consistent with the results of the study finding pollutants not filtered from the air. Additionally it is worth noting that achieving that result required not only large numbers of plants, but extensive care for the plants. The requirement that the plants be frequently cleaned of dust to keep their pores open may also be involved with the results. In any case, all these studies agrees that large numbers of plants are required to generate detectable results.