Malcolm McDowell Woods
Conscious Spaces

The humble houseplant is the best HVAC system

By - Dec 4th, 2009 01:24 pm
Sign-up for the Urban Milwaukee daily email
Put a houseplant on your desk, and remove 50% of molds and bacteria in your immediate breathing space.

Put a houseplant on your desk, and remove 50 percent of molds and bacteria in your immediate breathing space.

I’ve made a lot of new green friends lately. And I’m not talking about people interested in living sustainably. I’m speaking of plants. Yes, those ubiquitous potted stems with green foliage.

They’ve become a mandatory staple in all of my environments. And it’s not just because they’re aesthetically pleasing, although that’s often why I purchased them initially. It’s a well-established fact that living plants have a positive psychological effect on humans. They can improve one’s attitude, have a significant impact on productivity and job satisfaction, and help shorten recovery time for patients in hospitals. It’s been shown that visual exposure to plants has produced

Lyn Falk

Lyn Falk

significant recovery from stress within five minutes. But they do a lot more than all that. They’re busy working every minute to keep us — and our interior environments — healthy. They’re quite the valuable asset.

Clean air
You’ve no doubt heard or read the information the EPA has written about indoor air — that it can be 10 to 100 times more polluted than outside air. This is due to all the chemicals and pollutants emitted from our building materials and cleaning materials. Of course, a high tech, modern heat/cool air exchange/filtering/conditioning system is important and can correct a lot of problems, but we don’t all have these latest and greatest systems. That’s where plants come in. They can play a vital role in maintaining good indoor air.

Studies by NASA and other organizations have produced documented evidence that interior plants and their “root-associated microbes” can remove harmful chemicals from sealed chambers and can reduce the levels of airborne microbes in ambient air. For almost 20 years, Dr. Billy C. Wolverton, author of “How to Grow Fresh Air,” and his assistants in the Environmental Research Laboratory of the John C. Stennis Space Center in Mississippi have been conducting research using natural biological processes for air purification.

Wolverton has found that plants can greatly affect air quality in office buildings in which sick building syndrome* is common. For instance, commonly used office plants can remove the number one office toxin, formaldehyde, as rapidly as 1,800 micrograms per hour.

(*Studies have found that workers stayed home a minimum of 3.6 days — per employee per year — due to poor indoor air quality, causing a 12% reduction in productivity).

Research has shown plant-filled rooms contain 50 to 60 percent fewer airborne molds and bacteria than rooms without plants. Hospitals in Japan are adding “ecology gardens.”  Plants have been shown to reduce dust in a room by as much as 20 percent.

So who wouldn’t want plants around them?

How do plants clean the air?
Plant leaves absorb certain organic chemicals and destroy them through a process called “metabolic breakdown.”  In an article published by Green Plants for Green Buildings (, the process is described as follows: “When plants transpire water vapor from their leaves, they pull air down around their roots. This supplies their root microbes with oxygen. The root microbes also convert other substances in the air, such as toxic chemicals, into a source of food and energy. Microbes, such as bacteria, can rapidly adapt to a chemical contaminant by producing new colonies that are resistant to the chemical. As a result, they become more effective at converting toxic chemicals into food the longer they are exposed to the chemicals. It is also important to remember that the efficiency of plants as a filtering device decreases as the concentration of chemicals in the air decreases.”

Wolverton believes everyone should have a desktop plant, within what he calls the “personal breathing zone” where we spend most of our day. I extend the suggestion to the bedroom where our bodies are at rest and in a healing mode. Jay Naar, author of “Design for A Livable Planet,” believes 15 to 20 plants will clean the air in a 1,500 square foot area.


It’s important to clean your plants on a regular basis. Cleaning leaves helps remove clogging dust. Since it’s through the leaves that toxins are removed from the air, it’s important to keep their “pores” clean. Balsley recommends weekly cleaning by hand. Gently rub the top of the leaves. If you wait until you see dust on the leaves, you’ve waited too long. Spritzing the plant with water is OK if the pores have been opened, otherwise the water can simply run off the leaves. If you spritz, be sure the plant has time to thoroughly dry out between spritzes.

Going green?

Try these top 5 houseplants for a cleaner home

Much of this article is based on an interview with Stacey Balsley who works at Planteriors of Wisconsin in Waukesha. I was surprised to hear Balsley say that all of their indoor plants were from tropical climate zones and not native. But when she explained why, it made sense. Our native plants/trees need to go through a winter dormant period, which they can’t do when they’re in a heated environment.
So which plants do the heavy lifting when it comes to keeping our indoor environments healthy? Here are her recommendations:

Plant: Philodendron ‘Brasil’
Pollutant it Absorbs: Formaldehyde
Pollutant Sources: Plywood, carpeting, furniture, paper goods, household cleaners, foam insulation, particle board

Plant: Hedera canariensis (Algerian ivy)
Pollutant it Absorbs: Benzene
Pollutant Sources: Gasoline, tobacco smoke, synthetic fibers, plastics, inks, oils, detergents, rubber

Plant: Dracaena ‘Janet Craig’ compacta
Pollutant it Absorbs: Benzene
Pollutant Sources: Gasoline, tobacco smoke, synthetic fibers, plastics, inks, oils, detergents, rubber

Plant: Dracaena marginata (Dragon tree)
Pollutant it Absorbs: Trichloroethylene
Pollutant Sources: Dry cleaning, inks, paints, varnishes, lacquers, adhesives

Plant: Dracaena warneckii goldstar
Pollutant it Absorbs: Trichloroethylene
Pollutant Sources: Dry cleaning, inks, paints, varnishes, lacquers, adhesives

Categories: Uncategorized

Leave a Reply

You must be an Urban Milwaukee member to leave a comment. Membership, which includes a host of perks, including an ad-free website, tickets to marquee events like Summerfest, the Wisconsin State Fair and the Florentine Opera, a better photo browser and access to members-only, behind-the-scenes tours, starts at $9/month. Learn more.

Join now and cancel anytime.

If you are an existing member, sign-in to leave a comment.

Have questions? Need to report an error? Contact Us