"NASA environmental research has led to a plant-based air filtering system. Dr. B.C. Wolverton, a former NASA engineer who developed a biological filtering system for space life support, served as a consultant to Terra Firma Environmental."

  * http://ntrs.nasa.gov/search.jsp?R=982507&id=3&qs=Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=553055&id=4&qs=Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=958315&id=5&qs=Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=285936&id=7&qs=Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=140272&id=8&qs=Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=859981&id=1&qs=No%3D20%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=937505&id=5&qs=No%3D20%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=868996&id=7&qs=No%3D20%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=851731&id=10&qs=No%3D20%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * [[http://ntrs.nasa.gov/search.jsp?R=822211&id=1&qs=No%3D30%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1|Aquatic plants and wastewater treatment (an overview)]]
  * http://ntrs.nasa.gov/search.jsp?R=575277&id=3&qs=No%3D40%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1
  * http://ntrs.nasa.gov/search.jsp?R=246265&id=6&qs=No%3D50%26Ntt%3Dwolverton%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1

"Plants that top the clean-air list include peace lily, bamboo palm, English ivy, mums, and gerbera daisies" http://www.treehugger.com/files/2007/12/belair_filterin_1.php