15 The plants recommended by the NASA research for clean air are:
1. Philodendron scandens subsp oxycardium heartleaf philodendron (philodendrons come from tropical Americas and are related to arrowheads).
2. Philodendron domesticum, elephant ear philodendron.
3. Dracaena fragrans, varieties `Massangeana', `Janet Craig' and `Warneckii', cornstalk Dracaena, happy plant or Corn Plant, a relative of dragon trees from Africa.
4. Hedera helix, common ivy, which is also an outdoor plant originated from southern Europe.
5. Chlorophytum comosum, spider plant, a South African species.
6. Ficus benjamina, weeping fig tree, from southeastern Asia and Australia.
7. Epipremnum aureum, golden pothos, silver vine, devil's ivy, is a species coming from southeastern Asia and New Guinea, related to philodendrons.
8. Spathiphyllum x `Mauna Loa', a peace lily hydrid obtained from tropical American and Asian species.
9. Philodendron bipinnatifidum cut-leaf philodendron, tree philodendron, selloum, self-header from the rain forests of Paraguay and southeastern Brazil.
10. Aglaonema modestum, Chinese evergreen from southern China, related to philodendrons.
11. Chamaedorea sefritzii, bamboo or reed palm, a palm tree species originated from tropical Americas.
12. Sansevieria trifasciata, snake plant or mother-in-law's tongue, an African plant related to Butcher's broom.
13. Dracaena marginata , red-edged dracaena or Madagascar dragon tree.
14. Gerbera jamesonii, Gerbera daisy, from South Africa.
15. Chrysanthemum x morifolium, pot mums, a hybrid daisy from Asia.