You need about 1 sansiveria per hundred square feet or so. NASA has spent quite a bit investigating the efficiency and effectiveness of a wide array of plants f

You need about 1 sansiveria per hundred square feet or so. NASA has spent quite a bit investigating the efficiency and effectiveness of a wide array of plants for CO2 -> exchange. In an office you'll want plants such as bamboo palm, english ivy, peace lily, boston fern and a few others as they do their work presdominantly by day and sequester oxins such as formaldehyde and benzene. They don't have to fully supply everyone's oxygen to be effective, nor do they have to fully consume your CO2. That said, you'd be surprised at how well some of these will do just that. As a rule of thumb, about four mature sansevieria trificiata will convert as much CO2 to O2 as a single human does on a daily basis. But with those they are storing the CO2 by day and releasing O2 by night so while they will sck up the CO2 in your office by day, you won't see the O2 "come back" in that same time - at least not significantly so. Others such as some of the palms and lillies, and a few ferns, would do that same "effort" but in the daytime. Even then, in the context of offices and other rooms in this discussion the part to look at is their CO2 consumption, not the production of O2. Some plants, such as Ficus benjamina are very effective. One (or more) of those with a total leaf surface area of 1 square meter can take a closed room from 2,000ppm CO2 down to 400-500ppm in one hour (variance based on temperature and light levels).