Using Houseplants To Clean Indoor Air - University of Hawaii

1. Ornamentals and Flowers
(revised) Dec. 2007
OF-39
Using Houseplants To Clean Indoor Air
Kent D. Kobayashi, Andrew J. Kaufman, John Griffis, and James McConnell1
Department of Tropical Plant and Soil Sciences, 1University of Guam
n offices, homes, and other indoor areas, poor air Sulfur dioxide is especially a problem on the island
I quality can both cause health problems and make ex-
isting health problems worse. The U.S. Environmental
of Hawai‘i due to emissions from its active volcanoes,
and this “vog” can affect the other Hawaiian islands
Protection Agency currently ranks indoor air pollution when southerly (“kona”) winds spread it up the island
as one of the top five threats to public health. chain. Sulfur dioxide combines with atmospheric mois-
Indoor air pollution results from the release of chemi- ture to create sulfuric acid, which can severely burn the
cal vapors and the suspension in the air of particulates sinuses.
such as dust and microorganisms. In response to in- In construction, synthetic materials have replaced
creasing energy costs and the need to conserve energy many natural building materials and are a source of
resources, buildings and homes have been designed to be harmful and hazardous gases. Formaldehyde, used in
more energy efficient. Thus, many offices and new homes manufacturing many of these materials, is often a source
have tighter construction, sealing the building from the of indoor air pollution. Pressed-wood products, carpets,
outside air. This makes it easier for indoor air pollutants and surface finishes that are oil-based, solvent-based, or
to accumulate to dangerous levels. With people spend- alkyd-based are common building pollution sources.
ing up to 70–90 percent of their time indoors, long-term Household products and chemicals that cause indoor
exposure to indoor air pollution can cause various health air pollution include furniture waxes, paint strippers,
problems. adhesives, cleaning products, disinfectants, degreasers,
Air pollution can build up in any confined space, but and cosmetics. Some of these products release chemicals
gases from synthetic materials used these days to con- into the air during use, whereas others emit chemicals
struct or furnish offices and homes can, among other as they age, dry, or cure; this is known as out-gassing.
factors, result in “sick building syndrome.” While some Bioeffluents are emitted by people and household
people exposed to sick building syndrome will be unaf- pets through normal metabolic processes; these include
fected, others who are hypersensitive to the pollutants substances such as carbon dioxide, carbon monoxide,
can develop serious symptoms including eye, nose, and methane, alcohols, acetone, phenols, volatile fatty acids,
throat irritations, allergies, asthma, blurred vision, diz- ammonia, hydrogen sulphide, and nitrogen oxides.
ziness, fatigue, headache, skin irritation, nervous system
disorders, and upper respiratory and sinus congestion. Ways to improve indoor air quality
There are various ways to reduce indoor air pollution
Sources of emissions of air pollutants and improve air quality. Increasing ventilation and air
The major sources of indoor air pollutants are combus- exchange with the outside will help prevent the accu-
tion byproducts, building materials, household products mulation or reduce the amount of air pollutants indoors.
and chemicals, and bioeffluents. Combustion byproducts In the case of sulfur dioxide emitted by volcanoes, it is
include carbon monoxide, nitrogen and sulfur dioxides, advisable to close up the house if the vog episode is par-
formaldehyde, and tobacco smoke. Combustion byprod- ticularly bad. Exhaust fans can be installed in the kitchen
ucts are produced by gas ranges, cook tops, water heaters, and bathrooms, and air filters such as high-efficiency
clothes dryers, smokers, and internal combustion engines particulate air (HEPA) filters, which have a carbon filter
turned on in enclosed spaces. component, can be used. Combustion appliances should
Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in coopera­
tion with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mänoa, Honolulu, Hawai‘i 96822.
An equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, age, religion, color, national origin, ancestry, dis­
ability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. CTAHR publications can be found on the Web site <http://www.ctahr.hawaii.edu/freepubs>.

2. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Greenery can freshen the air and the ambience of an office workspace.
be vented directly to the outside and regularly inspected, Environmental Services have tested different houseplants
cleaned, and maintained. A byproduct of propane gas for their ability to remove various toxic gases such as
combustion is carbon monoxide. The house should be formaldehyde, xylene/toluene, and ammonia.
well ventilated when cooking or heating with propane. Plants absorb volatile organic compounds from the air
Use only wood products that are formaldehyde-free or into their leaves and then translocate them to their root
have low formaldehyde emissions. Seal the surfaces of zone, where microbes break them down. Microorgan-
wood products with surface finishes that are water-based. isms in the soil can use trace amounts of pollutants as a
Select low-emission building products and carpets. Avoid food source. Some organic chemicals absorbed by plants
household products that have hazardous vapors, and from the air are destroyed by the plant’s own biological
do not store hazardous products in the home. Product processes. The plant’s roots take up aqueous solutions
lines marketed as “eco-friendly” can be found at natural in the rooting media. Given that air also reaches plant
food stores and are becoming more readily available at roots, uptake by root tissues is another means by which
mainstream supermarkets. Air out carpeting and other air can be purified.
building materials before they are installed. Plants add aesthetic and biological comfort to interior
spaces. When plants are added to rooms, relative humid-
How houseplants help clean indoor air ity can increase and particulate matter (dust) accumula-
While developing technologies that allow humans to tion can decrease. Increasing relative humidity has a
live in closed environments such as the International relaxing effect on people, and removing dust aids by
Space Station, NASA discovered that plants help reduce reducing potentially allergy-inducing particles. Reducing
volatile organic chemicals/compounds (VOCs) and can particulate matter in a room may also be beneficial to
be an efficient way to filter the air in living compart- computers and other electronic equipment by limiting the
ments. The Plants for Clean Air Council and Wolverton amount of dust collecting on circuit boards and clogging
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3. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Table 1. Sources of some emissions that cause indoor air pollution.
Emission
Source Formaldehyde Xylene/toluene Benzene Ammonia Alcohols Acetone
Adhesives • • • •
Bioeffluents1 • • • •
Carpeting •
Caulking compounds • • • •
Ceiling tiles • • • •
Cleaning products •
Cosmetics • •
Draperies •
Electrophotographic • • •
printers
Fabrics •
Facial tissue •
Floor coverings • • • •
Grocery bags •
Nail polish remover •
Office correction fluid •
Paints • • • •
Paper towels •
Particleboard or chipboard • • • •
Photocopiers • • •
Pre-printed paper forms •
Stains and varnishes • • • •
Upholstery •
Wall coverings • • •
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Substances emitted by people through normal biological processes such as respiration.
Source: B.C. Wolverton, PhD; How To Grow Fresh Air; Penguin, 1997; used with permission.
air vents. offices and homes depends not only on their ability to
During photosynthesis, carbon dioxide is taken in clean the air but also on their growth habit, the ease of
through plant foliage, and oxygen is produced and re- growing and maintaining them, their light requirement,
leased by the plant as a byproduct. At night or when no and, of course, your personal taste.
photosynthesis is taking place, plants, like people, respire In an office or home, plants can have a profound influ-
and give off carbon dioxide. ence on peoples’ psychological well-being and serenity.
Volatile phytochemicals released by plant leaves ap- It has been shown that plants in living and work spaces
pear to be important in controlling airborne microbes have a measurable beneficial effect on people. Benefits
and mold spores in surrounding air. that have been documented where plants are added to the
Plants release water vapor via transpiration through the workplace include improved employee morale, increased
leaves and into the air, raising humidity. High transpiration productivity, and reduced absenteeism. In addition to
rates create convection currents that cause toxin-laden air plants adding beauty to a room and making it an invit-
to be pulled down into the soil around the roots, where ing place to live or work, research has found that when
microbes in the soil break down the gases into a source people are near or tending plants, they feel relaxed and
of food and energy. Air also moves into and out of leaf calm. Health and discomfort symptoms were found to
stomata (pore-like openings). It should be noted, however, be lower when indoor plants were present. These posi-
that higher humidity can lead to mold problems. tive factors also need to be considered in the selection
of appropriate houseplants.
Selecting houseplants Not all houseplants have been tested for their ability
Common houseplants that have been found to be effec- to clean indoor air. Of those tested, not all have proven
tive in cleaning indoor air are listed in the table on pages equally effective. It cannot be assumed that all harm-
4–5. Selection of houseplants to mitigate air pollution in ful pollutants can be removed by houseplants. While
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4. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Chemical Light
vapor require-
Plant name Description removal1 ment Remarks
Areca palm Clusters of erect, slender, 8 Sun to Releases an abundant amount of
(butterfly palm), cane-like stalks with feathery semi-sun moisture into the air. Fast growing.
Dypsis lutescens yellow-green fronds.
Bamboo palm, Clusters of small slender 9 Semi-sun Releases an abundant amount of
Chamadorea canes. Graceful fans with rich moisture into the air. Easy to care for.
elegans or C. green color.
erumpens
Boston fern, Stiff fronds arch outwards, 9 Semi-sun Releases an abundant amount of
Nephrolepis drooping downward as they moisture into the air. Ideal for hanging
exaltata age. baskets. Mist and water frequently to
reduce leaf drop.
Corn plant, Shiny medium green leaves with 8 Semi-shade Survives in dimly lit areas.
Dracaena a bold yellow-white stripe down Occasionally will send up a small
fragrans the center. Develops a solid spray of fragrant white flowers.
‘Massangeana’ woody stem. Leaves concentrate
at the top of each stem.
Dendrobium Has beautiful exotic blooms, 7 Semi-sun Flowers are long lasting.
orchid usually in clusters or in a row
along canes.
Dracaena Erect stems with a rosette of 8 Semi-shade Grows quickly. Tolerates dimly lit
deremensis broad, smooth, glossy, dark­ areas, but growth will be slow.
‘Janet Craig’ green leaves 12 inches long
and 2 inches wide.
Dracaena Leaves, 2 feet long and 2 6 Semi-shade Grows slowly. Tolerates low light and
deremensis inches wide, are green with dry air. Retains its variegation in low
‘Warneckei’ white and gray-green stripes. light.
Dragon tree, Smooth, gray, erect canes. 6 Semi-sun to Tolerates relatively low light and dry
Dracaena Leaves, 2 feet long and 1/2 semi-shade air.
marginata inch wide, are deep, glossy
green with red edges along the
margins. Leaves cluster at the
end of each cane.
Dumbcane, Wide, blotched green and white 7 Semi-sun to Fast growth.
Dieffenbachia (cream) leaves. Unbranched semi-shade
varieties* stems arch downward.
Dwarf date Stately main trunk with 9 Semi-sun Very slow grower. Adapts well to low
palm, Phoenix graceful, green fans that droop light levels.
roebelini elegantly. Fronds reach 3 feet
and grow horizontally.
English ivy, Vigorous climber which sends 9 Semi-sun to Easy to grow. Ideal for hanging
Hedera helix* out aerial roots that attach to semi-shade baskets. Generally does not do well in
any surface. Dark green leaves high temperatures.
have 3 to 5 lobes.
Ficus Slender dark green leaves. 7 Full sun and Easy to grow. May have some leaf
bennendijkii ‘Alii’ semi-sun drop until it adjusts to its new location.
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5. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Florist’s mum, Produces a brilliant display of 9 Full sun and Avoid midday sun as the heat may age
Chrysanthemum colorful flowers. semi-sun. the blossoms prematurely.
morifolium
Gerbera Sturdy stems that have colorful 9 Full sun and Releases abundant moisture into the
daisy, Gerbera flowers. Leathery leaves. semi-sun air. Avoid midday sun as the heat may
jamesonii age the blossoms prematurely.
Golden pothos, Vine with green heart-shaped 5 Semi-shade One of the easiest houseplants to
Epipremnum leaves with gold or cream to shade grow. Fast growth. Can be grown as a
aureum colors. hanging basket or trained to climb.
Kimberley Fern with graceful, drooping 9 Semi-sun to Releases an abundant amount of
queen fern, fronds and lush green foliage. semi-shade moisture into the air. Mist and water
Nephrolepis regularly to reduce leaf drop.
obliterrata
King of hearts, Dark, olive-green, oval-shaped 7 Semi-shade Slow growing. Can be difficult to
Homalomena leaves with areas of silver or to shade maintain.
wallisii cream. Leaves 8 inches long.
Lady palm, Large palm with fans 6 to 12 7 Semi-sun Grows slowly. One of the easiest
Rhapis excelsa inches wide with 4 to 10 thick houseplants to care for.
or R. humilis shiny leaves. Brown hairy main
trunk with thin arching stems.
Lily turf, Liriope Grassy arching evergreen 7 Semi-sun to Produces small spikes of white or
muscari leaves reaching 6 to 18 inches semi-shade lavender flowers.
long. May be dark green or
variegated.
Peace lily Sends up stiff erect stalks that 8 Semi-shade Releases an abundant amount of
(White flag), produce beautiful white spathes. to shade moisture into the air. Tolerant of low
Spathiphyllum Dark green leaves stand erect light. Will bloom indoors.
varieties in the juvenile stage, but start to
bend as they mature.
Philodendron Vining habit. Burgundy-red 6 Semi-shade Easy to grow. Needs to be staked or
erubescens* leaves are long and narrow with to shade. given support for climbing.
‘Red Emerald’ yellow veins.
Rubber plant, Thick, leather-like, glossy, 9 Semi-sun to Easy to grow. Tolerates low light.
Ficus elastica* dark-green leaves that contain semi-shade.
a rubber-like latex.
Schefflera Has long stems with 7 to 16 8 Semi-shade. Easy to grow.
(umbrella tree), deep green leaves, each up to
Brassaia 12 inches long.
actinophylla*
Spider plant Sends up slender, arching 6 Semi-sun to Ideal for hanging baskets. Has small
(airplane plant), shoots with leaves that may be shade. white flowers at the end of aerial
Chlorophytum green or green with a broad runners, which are followed by
comosum center stripe of yellow or cream. airborne plantlets.
Leaves 6–12 inches long.
Weeping fig, Treelike growth habit. Graceful 8 Full sun to Leaf drop is common until it adjusts to
Ficus drooping branches. Small, dark semi-sun. its new environment.
benjamina* green, pointed, glossy leaves.
Rating 1 to 10, with 10 being excellent. *May be hazardous or toxic if eaten or comes in contact with eyes or skin; keep plants away from children.
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6. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Extensive use of plants in an indoor setting can create the feeling of outdoors; this indoor greenhouse-
type structure is in a botanical garden on Awaaji Island near Osaka, Japan.
houseplants are not a “total solution” to improving indoor Gilhooley, M.J. 2002. Horticulture in health care: the
air quality, they should not be overlooked as an aid in role of plants in health care facilities. Health Facilities
creating interior spaces conducive to the health of those Management, February 2002. 4 p.
who occupy them. Goodwin, G.A., and V.I. Lohr. 1993. Interior plants in a
classroom improve air quality and the learning envi-
Acknowledgement ronment. HortScience 28:491.
Thanks to Scot Nelson and Edwin Mersino for their Lohr, V.I., G.K. Goodwin, and C.H. Pearson-Mims.
review of the manuscript. 1994. Effects of interior plants on relative humidity
and air-borne particular matter in indoor environ-
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7. UH–CTAHR Using Houseplants To Clean Indoor Air OF-39 — Nov. 2007
Large interiorscape plantings combined with pools or fountains greatly enhance the ambiance of an office
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