Cost Effective Air Cleaning Plants

House plants can help purify the air by removing toxic chemicals as well as kill mold spores and bacteria in the air by producing negative ions. Here's a look at the most cost effective plants from the NASA Clean Air Study.

I recently ordered about a  dozen houseplants online in a mix of sizes from 2" to 6" pots. After I received them I set them all up in a warm room where they got a lot of indirect light so they could recover from shipping. After a couple of hours I entered the room again and I could instantly smell the effect of the negative ions produced by the plants. It was the same clean smelling air that I get if I have the ionizer on one of my HEPA purifiers on and plants save money on electricity and filter costs. You'll need to periodically wipe dust off the leaves or bring them to a shower for a good rinse.

There are a lot of web pages published with information regarding the plants in the study on the big content mills. As is quite often the case with some of these sites that hire writers that may or may not have a good understanding of the subject there are some misunderstandings or misrepresentations on what the study actually says which is why I wanted to write this article. In addition I wanted to take a different look at which plants are the most cost effective at removing toxins.

All Plants Remove Toxins

That's right all plants will improve your indoor air quality by removing toxins. At least that's the basic assumption. It's not just the dozen or so plants identified in the NASA Clean Air Study or other research. And it's not just the plants. A good portion of that air purifying power comes from the microorganisms that colonize in the soil around the roots!

So why did the NASA study only list 12 plants? To answer that you first have to understand that NASA was looking into options for cleaning the air in sealed space habitats that may house astronauts for long missions.

It doesn't look like they tested thousands, hundreds or even dozens of plants looking for which plants remove the most toxins. Instead it appears that they selected primarily a number of low-maintenance plants with low light needs and ran tests to see how well they performed against three common toxins found in building materials. These types of low-light, low-maintenance plants are not just great for space pods but work well as plants for homes and offices.

There's nothing really special about these plants in general and some of them weren't necessarily all that effective or at least not that efficient at removing toxins. What is different is that someone did the tests on these plants to see how well they perform. The twelve plants in the study are:

Common Name	Scientific Name	Order From
Bamboo palm	Chamaedorea seifritzii	Hirt's ebay
Chinese evergreen	Aglaonema modestum	Home Depot Hirt's ebay
English ivy	Hedera helix	Home Depot Hirt's ebay
Ficus	Ficus benjamina	Home Depot Hirt's ebay
Gerbera daisy	Gerbera jamesonii	Home Depot ebay
Janet Craig	Dracaena deremensis "Janet Craig"	Hirt's ebay
Marginata	Dracaena marginata	Home Depot Hirt's ebay
Mass cane/Corn cane	Dracaena massangeana	Home Depot Hirt's ebay
Mother-in-law's tongue	Sansevieria laurentii	Home Depot Hirt's ebay
Peace lily	Spathiphyllum "Mauna Loa"	Home Depot Hirt's ebay
Pot mum	Chrysanthemum morifolium
Warneckei	Dracaena deremensis "Warneckei"

Dr. B.C. Woverton has continued to study how plants clean the air and has published a book on the subject which identifies how more plants clean toxins called How to Grow Fresh Air: 50 House Plants that Purify Your Home or Office
If you have specific concerns about toxins in your home or office you should have the air assessed and get the appropriate types and quantity of plants that have been shown to remove those toxins. After you've had the plants in your environment you should follow up with another test to see how well the plants are performing. In general though 1 to 2 plants per 100 square feet is a good guide with more plants in rooms you're in most often.

Toxin Removal Cost Effectiveness

The NASA study indicates the how well a single plant removed specific toxins. The three they tested for were Benzene, Trichloroethylene and Formaldehyde. Each plant was set up in a sealed container with a fan to circulate the air and a known quantity of toxin was introduced into the chamber. Readings of the level of toxins in the chamber where measured before and after a 24 hour period to see how much toxins the plants removed.

By looking at the data from the NASA Clean Air Study I was able to calculate how efficient each plant was at removing that toxin in terms of micrograms of toxin removed per plant leaf area.

Another calculation was to determine how many plants would be required to remove 25,000 micrograms of that toxin based on the recorded results. Comparing that value with the current market price of the plant we can see which plants will give you the best bang for the buck.

The NASA study didn't include container size for each plant so I'm just assuming common pot sizes for the given plants as would be sold by most nurseries. For that reason, and because not all plants are identical, these numbers should just be used as a rough guide.

Formaldehyde

The highest concentration of toxin in your home or office air is likely formaldehyde. It's in a lot of building materials, furniture, paper products, cosmetics, deodorants, shampoos, cleaning products, released by burning gas, kerosene or smoking cigarettes and it's even in new clothes.  If you bought Chinese manufactured laminate flooring from Lumber Liquidators it's apparently a big problem according to a recent 60 minutes report. The following table lists the plants from the study.

Plant	Leaf Surface Area (cm2)	µg Removed	µg/area	Plants per 25k µg	Price	Price per 25k µg
Bamboo palm (Camaedorea seifritzii)	14,205	76,707	5.4	0.3	$20.98	$6.84
Janet Craig (Dracaena deremensis “Janet Craig”)	15,275	48,880	3.2	0.5	$22.98	$11.75
Snake Plant (Sansevieria laurentii)	2,871	31,294	10.9	0.8	$19.98	$15.96
Marginata (Dracaena marginata)	7,581	20,469	2.7	1.2	$17.98	$21.96
Peace lily (Spathiphyllum “mauna loa”)	8,509	16,167	1.9	1.5	$18.98	$29.35
English Ivy (Hadera helix)	985	9,653	9.8	2.6	$16.98	$43.98
Banana (Musa oriana)	1,000	11,700	11.7	2.1	$24.98	$53.38
Green Spider Plant (Chlorophytum elatum)	2,471	10,378	4.2	2.4	$26.98	$64.99
Elephant Ear Philodendron (Philodendron domesticum)	2,323	9,989	4.3	2.5	$25.98	$65.02
Heart Leaf Philodendron (Pilodendron Oxycardium)	1,696	8,480	5.0	2.9	$23.98	$70.70
Golden Pothos Scindapsus aureus	2,723	8,986	3.3	2.8	$27.98	$77.84
Lace Tree Philodendron (Philodendron solloum)	2,373	8,656	3.6	2.9	$28.98	$83.70
Chinese Evergreen (Aglaonema “silver Queen”)	1,894	4,382	2.3	5.7	$21.98	$125.40

Notice how the amount of toxins removed (in micrograms) per leaf surface area varies widely indicating some plants are much more efficient than others at removing formaldehyde. That alone isn't a good indicator of how cost effective the plant will be since the size of a plant varies by type. By looking at how many plants are required to remove 25k micrograms of formaldehyde and comparing that to the cost of plants we can see that the Bamboo Palm is going to give you the most formaldehyde removal for your money. Even though the Banana plant has a very high µg/area it is not very cost effective because each plant doesn't have a lot of leaf area. But it's the only plant on the list that produces an edible fruit.

For some reason Goldon Pothos gets brought up a lot, even by the primary researcher Dr. Wolverton, but there isn't much data on it in the report and what is there regarding formaldehyde doesn't look that impressive to me.

Benzene

This nasty volatile organic compound comes from a variety of different sources. One of the biggest sources is cigarette smoke but it's also found in paints, adhesives, paint removers and is emitted from car exaust as well as burning other fuels.

Leaf Surface Area (cm2)	µg Removed	µg/area	Plants per 25k µg	Price	Price per 25k µg	Leaf Surface Area (cm2)
Gerbera Daisy (Gerbera jamesonii)	4,581	107,653	23.5	0.2	$10.99	$2.55
Pot Mum (Chrysanthemum morifolium)	4,227	76,931	18.2	0.3	$19.98	$6.49
Peace lily (Spathiphyllum “mauna loa”)	7,960	41,392	5.2	0.6	$12.98	$7.84
Warneckii (Dracaena deremensis “warneckii”)	7,242	39,107	5.4	0.6	$14.65	$9.37
Bamboo palm (Camaedorea seifritzii)	10,325	34,073	3.3	0.7	$16.98	$12.46
Marginata (Dracaena marginata)	7,581	30,324	4.0	0.8	$16.98	$14.00
Snake Plant (Sansevieria laurentii)	2,871	28,710	10.0	0.9	$16.98	$14.79
Janet Craig (Dracaena deremensis “Janet Craig”)	15,275	25,968	1.7	1.0	$16.98	$16.35
Chinese Evergreen (Aglaonema “silver Queen”)	3,085	14,500	4.7	1.7	$11.98	$20.66
English Ivy (Hadera helix)	1,336	13,894	10.4	1.8	$14.98	$26.95

The clear winner here is the Gerbera Daisy. The plants are relatively small yet remove a large amount of benzene. The downside of the Gerbera Daisy is that it requires more care and light than the other plants on the list.

The peace lily does quite well at removing benzine for the price and is one of my favorite house plants. I spent a couple of months away from home, only visiting every few weeks and a peace lily I had in a corner away from any light was still alive in spite of the neglect. A little water and it recovered quickly.

Snake plants are also very easy to care for and don't take up much space for the amount of air purifying they do. They're great for bedrooms since unlike other plants it converts carbon dioxide into oxygen at night instead of during the day.

Trichloroethylene

Sources of trichloroethylene are glues, adhesives, paint removers, spot removers, rug cleaning fluids, paints, metal cleaners and typewriter correction fluid. It can even enter your home through water.

Leaf Surface Area (cm2)	µg Removed	µg/area	Plants per 25k µg	Price	Price per 25k µg	Leaf Surface Area (cm2)
Gerbera Daisy (Gerbera jamesonii)	4,581	38,938	8.5	0.6	$10.99	$7.06
Peace lily (Spathiphyllum “mauna loa”)	7,960	27,064	3.4	0.9	$12.98	$11.99
Marginata (Dracaena marginata)	7,581	27,292	3.6	0.9	$16.98	$15.55
Janet Craig (Dracaena deremensis “Janet Craig”)	15,275	18,330	1.2	1.4	$16.98	$23.16
Bamboo palm (Camaedorea seifritzii)	10,325	16,520	1.6	1.5	$16.98	$25.70
Warneckii (Dracaena deremensis “warneckii”)	7,242	13,760	1.9	1.8	$14.65	$26.62
Mass cane (Dracaena massangeana)	7,215	10,101	1.4	2.5	$16.98	$42.03
Snake Plant (Sansevieria laurentii)	3,474	9,727	2.8	2.6	$16.98	$43.64
English Ivy (Hadera helix)	981	7,161	7.3	3.5	$14.98	$52.30

Again the Gerbera Daisy is the winner again in terms of effectiveness and cost. They're also very popular for their beautiful blooms.