Safer Indoor Air Using Air-Cleaning House Plants, Dust-Control Filters, and Other Methods

Introduction | Hazards of Indoor Air Pollution | Air Cleaning-House Plants | Air Filtration


Although smog, belching factory smoke stacks and auto-exhaust emissions get ample attention from the press, media and pollution activists (and rightly so), the simple fact is we spend 90 percent of our time indoors. Hence, the quality of indoor air is, in many ways, more important for our health and longevity than outdoor air. The concentration of pollutants per unit of air can be 10 to 50 times greater indoors than outside. Recent scientific research1,2,3,4 leads many public-health experts to conclude that indoor air pollution is one of the biggest environmental risks we face. Yet, it is one of the least studied, most poorly regulated areas of public health. top of page.

Hazards of Indoor Air Pollution and Dust Particles

The concentration of pollutants can be higher indoors than out. Why? One reason is because indoor environments have a limited volume of air; therefore, low levels of pollutants can lead to higher concentrations per breath. Indoor environments have less exchange with fresh air than the air outdoors. Additionally, the range of indoor environments and the wide variety of products we use indoors throw at us a much more diverse plethora of pollutants. Finally, indoor environments often have higher levels of humidity and moisture -- conditions that intensify or amplify some pollutants like biological organisms, which grow better in the presence of moisture.

Indoor Air Pollutants and Their Effects (adapted from a Table in Risk3)
Pollutant Potential Health Effects
Environmental "secondhand" tobacco smoke Immediate: Respiratory irritation, respiratory infection in children, decreased lung function, eye irritant
Delayed: Lung cancer, heart disease, chronic respiratory health problems
Radon Immediate: none
Delayed: lung cancer (but, comparatively, much higher rate in smokers)
Carbon monoxide (CO) Immediate: low levels of nausea, fatigue, headache, chest pain in people with heart disease; high levels of impaired vision, dizziness, confusion, seizures, brain damage, death
Delayed: none
Nitrogen dioxide Immediate: Respiratory irritation,impaired lung function, increased respiratory infection in children
Delayed: may contribute to asthma
Organic gases Immediate: eye, nose and respiratory irritation; headaches; nausea
Delayed: at higher levels, damage to liver, kidneys, central nervous system; possibly cancer
Bacteria, viruses Immediate: influenza and other airborne infectious diseases, infections, digestive problems, "humidifier fever"
Delayed: none
Molds, mildew, fungi Immediate: eye, nose and respiratory irritation; skin rash, allergic reactions; hypersensitivity pneumonitis
Delayed: none
Animal dander, dust mites, cockroach residue, pollen from indoor plants Immediate: allergic reactions, asthma attacks
Delayed: may contribute to onset of asthma
All pesticides Immediate: eye, nose and respiratory irritation
Delayed: at high levels, damage to central nervous system and kidneys, small increased cancer risk
Asbestos Immediate: none
Delayed: asbestosis, lung cancer
Particles Immediate: eye, nose, and respiratory irritation; asthma attacks; increased respiratory infection; chest pains; heart arrhythmia; heart attack
Delayed: none
Lead Immediate: none (acute lead poisoning)
Delayed: impaired mental functioning, especially in children, impaired hearing and motor control, decreased growth rate, behavior problems, impaired vitamin D metabolism; at higher levels, kidney damage, anemia, severe brain damage, coma, death
top of page

Tip: Careful Where Your Breathe

EPA's Safe Upper Limit For Carbon Monoxide (in parts per million, ppm): 9

In our daily routines, are we ever exposed to dosages above 9 ppm? Yes. Here are some examples:

  • Enclosed Parking Garage: 18 ppm
  • Kitchen (Fumes While Cooking, with exhaust fan running): 11-12 ppm

Air-Cleaning House Plants

House plants not only convert carbon dioxide to oxygen but also trap and absorb many pollutants. Many of these chemical compounds are released into our air through a process called "off-gassing" and often come from everyday items present in our homes and office. NASA discovered over 300 organic compounds aboard the space shuttle and, in it's endeavor to conquer space, began testing common house plants for their capacity to purify indoor air. Luckily for us it turns out that some of the best house plants for cleaning our air are also very easy to grow.

Tests conducted by NASA have conclusively demonstrated that many common houseplants remove pollutants during their natural process of photosynthesis: while plants take in carbon monoxide, they also pick up airborne pollutants through small openings called stomates in the leaves. They're very effective at removing gases such as carbon monoxide, carbon dioxide, benzene, cigarette smoke, formaldehyde, and ozone. These gasses are harmful for us to breathe, but serve as food for a plant (symbiosis in action!). Aloe vera (which is a good plant to have around to treat burns and skin irritations), bamboo palm, common chrysanthemums, dracaena palms, philodendrons, golden pothos, spider plants, and scheffleras make the best air filters. It takes one or two good sized plants to purify the air in a 10 x 10 room, depending on the level of pollutants present.

Although it should be safe to presume that all plants are capable of removing toxins from our air, research by NASA showed that some house plants are more efficient in filtering out toxins than others. Philodendrons, Spider plants, and Pothos were found to be the most efficient in the removal of formaldehyde. Gerbera Daisies and Chrysanthemums were found to be effective in the removal of benzene, a known carcinogen.

Generally, allow one houseplant per 100 square feet of living area. The more vigorous the plant, the more air it can filter. Keep in mind that plants will not do much to alleviate tobacco smoke in the air.

Here are the top four best house plants for purifying air. These choices are based on content gleaned from myriad print and Internet resources.

Scorecard: 8.5 Name: Areca Palm (Chrysalidocarpus lutescens)
Chemical Vapor Removal: 8 Areca Palm (Chrysalidocarpus lutescens)
Maintennance/ease-of-growth: 8
Plant durability (resistance to diseases and insects): 8
Transpiration rate: 10

Scorecard: 8.5 Name: Lady Palm (Rhapis excelsa)
Chemical Vapor Removal: 7 Lady Palm (Rhapis excelsa)
Maintennance/ease-of-growth: 9
Plant durability (resistance to diseases and insects): 10
Transpiration rate: 8

Scorecard: 8.4 Name: Bamboo Palm (Chamaedorea seifrizii)
Chemical Vapor Removal: 9
Bamboo Palm (Chamaedorea seifrizii)
Maintennance/ease-of-growth: 8
Plant durability (resistance to diseases and insects): 8
Transpiration rate: 9

Scorecard: 8.0 Name: Rubber Plant (Ficus robusta)
Chemical Vapor Removal: 9
Rubber Plant (Ficus robusta)
Maintennance/ease-of-growth: 9
Plant durability (resistance to diseases and insects): 8
Transpiration rate: 7

top of page

Highly Recommended Reading

How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office. Author: B. C. Wolverton
How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office by B. C. Wolverton

Amazon Reviews:

"The book is laid out beautifully. The 50 plants are listed by rank based on removal of chemical vapors, ease of maintenance, resistance to insect infestation, and transpiration rate. Each plant gets a two-page spread; one page discusses the plant's ideal environment, sunlight conditions, care, and general information about the plant along with a full photo of it. The next page has a zoomed-in full-page photo of the leaves and/or flowers so the reader gets a feel for what the plant looks like and how it will fit with their decor.

"The book begins by discussing the research about the air purification qualities of houseplants. The initial chapters explain how air contaminates enter our homes, the adverse effects these toxins have on humans, and how plants remove the contaminates from the air. I was surprised to learn that common household items such as blankets, toys, gas stoves, computers, and carpets can lead to allergies, asthma, even cancer, and that they might contribute to Sudden Infant Death Syndrome (SIDS). Once I read how certain plants can remove these dangerous microbes from the air, my husband and I immediately discussed adding these plants to our home.

'The author explains in great detail how to care for the plants, which I found very helpful as a novice indoor gardener. The author also details the specific toxins that different plants remove, and indicates whether the plants transpire at night (which is good for a bedroom) or during the day."


"This is a beautifully put-together book focusing on a unique aspect of plant ownership. Entries include both a full-on picture of a healthy, attractively potted specimen, plus a close-up detail of leaves and /or flowers. Descriptions of plant care are concise, well organized and accompanied by a more generalized description of the plant and particulars. Each plant is rated on four characteristics (removal of chemical vapors, ease of growth and maintenance, resistance to insect infestation, and transpiration rate), using an easy to read bar chart which appears on the same page as the description and picture.

This book is an excellent addition to an avid collector's plant library, both for its curiosity value and beautiful coverage of basic houseplants, and doubtless of interest to people concerned about air quality as well. It also provides enough basic information on each plant to be a useful reference for beginning enthusiast, but I would qualify that by saying that newbies will probably want a more broadly based work as their first home reference guide. For people looking for gift books, the pictures and layout are lovely."


"This book not only gives concise, quantitative data about which substances each plants removes from the air, but combines this data with other factors like ease of care and pest resistance to give one overall ranking to each plant. The introduction is fascinating, especially the part about his eco-house which uses plants to clean his water waste as well as the air. However, what I like best about the book is the gorgeous pictures. I have never seen a plant book with such large, glossy pictures of such perfect plants matched with the ideal pot. It's beautiful!"


Clearly written jargon-free guide to growing helpful plants
"I found this book well-written and easy to use. It helped me select the right plants and learn how to grow them. I currently have about 25 plants, and they are all low maintenance and problem-free. My indoor air quality has improved, and my house looks great with so many green plants of all shapes and sizes."


A must read for people with allergies
"I have been evaluated by a specialist in environmental issues. He suggested that I buy a few houseplants and even gave me a list. However, as a person with absolutely NO indoor plants before this, I needed more info. This book is absolutely the one I needed. It gives more than enough data about taking care of wonderful houseplants - complete with pictures. I highly suggest this book for anyone, especially those with environmental problems. BUY!!!"

Click here to buy How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office

What Else Can Be Done To Make Indoor Air Safer?

Eliminate the source of pollutants. The most sustainable choice would be to eliminate indoor air pollutants altogether, so there would be no need to collect toxic pollutants in filters and then dispose of them somewhere else in the ecosystem. Air-purification devices can reduce the amount of pollutants present in a closed indoor space, but don't assume that plants and machines can remove pollutants 100% or that the quality of the air is equivalent to fresh, clean outdoor air in a pristine place. Particleboard furniture and cabinets, cleaning products, pesticides, plastics and synthetic fibers used in furnishings and other construction, carpeting, drapes, scented items, gas appliances and heaters, and many other common items made from petrochemicals all contribute to an increase in indoor air pollution.

Ventilate. Simply opening a window will allow many pollutants to escape. Opening two windows on opposite sides of a room or house will create a crossdraft that will clear the air faster and more completely. If you need more ventilation but don't want to lose heat, use an AIR-TO-AIR HEAT EXCHANGER. Remember: even if the outside air is polluted, concentrations are probably not has high as they are inside. Your sense of smell will come in handy here: if you smell diesel or other fumes outside, then wait a bit before opening the window again.

Carbon and/or HEPA air filter for removing volatile gases and/or particles. Carbon alone will remove gases (misty vapors of volatile chemicals such as formaldehyde, plastics, paints, solvents, pesticides, and perfumes), HEPA alone will remove particles (bits of pollen, dust, mold, and animal dander); together they give the highest efficiency broad spectrum removal.

Activated carbon used in filters works by adsorption, a process by which pollutant gases are attracted by and stick to the carbon. There are several types of activated carbon; coconut shell carbon is generally considered to be the highest quality. Filters can also contain other filter media that have special qualities. Some coconut-shell carbon is impregnated with non-metal salts to increase efficiency in removing formaldehyde--up to 90 percent. Carbon can also be combined with Purafil, a nontoxic odoroxidant made of activated alumina impregnated with potassium permanganate. Purafil works by both absorbing and adsorbing gases and then destroying them by oxidation. This combination is more effective that carbon alone, but not as effective as impregnated carbon.

High-Efficiency Particulate Arrestance (HEPA) filters work by trapping particles mechanically. They are rated at 99.99 percent efficiency for particles 0.3 microns in size (dust, pollen, and plant and mild spores). Developed by the Atomic Energy Commission during World War II to remove radioactive dusts from industrial exhausts, they are paper-like filters made of randomly positioned fibers that create narrow passages with many twists and turns. As the air passes through, particles are trapped, clogging holes and making the grid smaller, which enables the filter to be even more efficient with ongoing use.

Activated carbon and other filter materials must be changed regularly. How often you'll need to change them depends on how many hours a day the filter is used and how polluted the air is, so it is impossible to predict how long filter media will last. Manufacturers estimate that activated carbon will last about two thousand hours, or twelve hours per day for six months; under normal use the carbon should last six to nine months. Pre-filters are generally changed more frequently, and HEPA filters last for several years.

Air filters can be purchased as portable models, or you can have them built into your central heating/air conditioning system. An important point to remember is that the cleaning capabilities of any portable unit are generally limited to the air in the room in which it is being used. And as with air-conditioning, air cleaners are most effective if no outside air is entering from adjacent rooms, open windows, or central air systems.

Each air purification unit is designed to effectively remove pollutants from the air contained in a certain measured space. The amount of filter media the unit contains, the rate at which the air flows through the media, the size of the motor, and all other aspects of the unit's design are geared to the designated room size. You may need several filters to continuously clean the air throughout the house, or a unit portable enough to be easily moved from room to room. The small air cleaners found in most department, drug, and discount stores are inexpensive and convenient, but do not contain sufficient carbon to effectively clean the amount of air that passes through.

Truly effective portable air filters are rarely sold in stores, but are available via mail or Internet order (see below). For a built-in whole house filter, check the Yellow Pages for a Heating, Ventilation, and Air Conditioning (HVAC) dealer. top of page

Honeywell 12528 Enviracaire HEPA Air Cleanericon
Honeywell 12528 Enviracaire HEPA Air Cleanericon
List Price: $219.99
Our Price: $124.90
Save: $95.09 (43%)
Honeywell 50257 Enviracaire HEPA Air Cleaner
List Price: $150.00
Our Price: $69.99
Save: $80.01 (53%)
Honeywell Enviracaire SilentComfort Air Cleanericon
Honeywell Enviracaire SilentComfort Air Cleaner
List Price: $199.99
Our Price: $79.99
Save: $120.00 (60%)

Negative ion generators. As air cleaners, negative ion generators are quite limited -- they will precipitate only certain small particles. While practically useless for dust or pollen, they are very effective at removing the particles found in cigarette smoke and smog, cleaning the air so that it becomes clear and odorless. But they cannot remove the invisible, odorless toxic gases that are also present in cigarette smoke and smog. Negative ion generators and ionizers should be purchased for their health benefits or for use with activated carbon filters for removal of cigarette smoke, but not as broad spectrum air cleaners. If you do purchase an ionizer, choose one with a built-in particle collector, so you won't end up with black particles stuck to your walls. top of page

Hoover SA2000 Silent Air Ionic Air Purifiericon
Hoover SA2000 Silent Air Ionic Air Purifiericon
List Price: $249.99
Our Price: $99.99
Save: $150.00 (60%)
Hoover SA4000 Silent Air Ionic Air Purifiericon
Hoover SA4000 Silent Air Ionic Air Purifier
List Price: $349.99
Our Price: $139.99
Save: $210.00 (60%)

Electrostatic filters. Electrostatic filters attract particles by electricity -- either by way of an electronic air cleaner (electrostatic precipitator) or with electronically charged plastic fibers (electret). Generally, neither type is recommended. Electrostatic precipitators are rarely more than 80 percent efficient and can quickly drop to 20 percent efficiency. They also produce ozone and positive ions, and must be cleaned often with volatile petrochemical solvents. Electret, on the other hand, is extremely efficient for removing particles, but is a petrochemical product and gives off a strong odor. top of page

Highly-Recommended Reading

Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You
Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You
by David Ropeik, George Gray "WE LIVE in a dangerous world..."

From Publishers Weekly
For those who can't find enough time in a day to worry about all of life's possible dangers, there's a new book to help them prioritize. Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You is a fascinating assessment of the level of threat posed by various illnesses, accidents, environmental pollutants and other factors. David Ropeik, director of risk communication at the Harvard Center for Risk Analysis, and his colleague George Gray, a toxicologist, evaluate such real or perceived menaces as cell phones, biological weapons, pesticides, mad cow disease and medical errors. For each entry, they analyze the potential hazards and offer tips for reducing risk. They also include a "Risk Meter"-a chart that shows likelihood of exposure and severity of consequences at a glance. 25 b&w illus. Copyright 2002 Reed Business Information, Inc.

Book Description:
An indispensable and timely guide, Risk is the authority for assessing threats to your health and safety.

We continually face new risks in our world. This essential family reference will help you understand worrisome risks so you can decide how to stay safe and how to keeps risks in perspective. Expert authors David Ropeik and George Gray include information on:

- 50 top hazards
- your likelihood of exposure
- the consequences
- ways to reduce your risk

They cover topics such as:

- cancer
- biological weapons
- indoor air pollution
- pesticides
- radiation

Amazon Reviews:

This is the scientific facts without the hype
This is an excellent book on the subject of risk analysis focused on 48 specific risks we encounter in everyday life. The book is divided in three parts. Part I describes mainly discretionary or behavioral risks. These consist mainly of risks we choose to incur such as smoking, drinking alcohol, and drinking coffee. Part II focuses on environmental risks. These are risks that we bear, and for the most part can't avoid such as water and air pollution. Part III describe Medical related risks. As the authors specify these are often more outcomes than risks. For instance, cancer and heart disease are not direct risks, they are outcome of a combination of deficient nutrition, bad lifestyle habits (lack of exercise), and inherited genes.

The authors make an excellent effort to come up with the most current and objective scientific knowledge. They avoid all the hype in the media that may exaggerate or understate various risks. After reading this excellent book, it is interesting to notice that by far the biggest risks to our health and survival are the behavioral risks or the risks we choose to undertake. These include smoking, drinking, obesity, and also sun tanning. These risks are far greater than pesticides, water pollution, air pollution, electro magnetic fields, and radiation from cellular phones. Thus, the authors do a good job to strengthen our common sense based on scientific evidence instead of going crazy due to misinformation by the media.

The book is excellent for several reasons. First, the authors have a solid scientific background themselves. Second, they fully recognized that no matter how smart you are, you just can't be the number one expert in everything. Thus, each of the chapters (dedicated to any one of the specific 48 risks) has been fully reviewed by one or more of the top authorities in the relevant field covered. Therefore, the book does not reflect just their opinions. In essence, each of their risk analysis has been peer-reviewed by the top specialists. Third, they provide excellent reference at the end of each section to credible websites where you could further research specific issues if you cared too. Fourth, they came up with a self explanatory Risk Meter that is a visual representation of the specific exposure to a certain risk, and severity of consequence if you are exposed to this same risk. Thus, very quickly you can get a read on how serious a specific risk is right at the beginning of each chapters. Fifth, in the Appendix 2, the authors summarize their opinions on all 48 risks. So, if you just wanted to know the bottom line on a series of rather complex risks, you could quickly refer to this Appendix, and in seconds you can figure how material these risks are to yourself.

This is definitely an excellent reference book. It is probably not the type of book you read in a sequential fashion cover to cover. Only the Ben Stiller character (a neurotic risk assessment specialist working for a life insurance company) in the comedy "Along Came Polly" would. I admit, I am like this character, and I managed to read about 29 of the 48 risks straight through. But, that is just me. I am a bit nuts about that stuff. You'll probably get a lot more by referring to the book whenever the media, or the experience of a friend or relative triggers within you a health-risk issue you want to know more about.

CLICK HERE to order: Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You

References and Resources

  1. "Everyday Exposure to Toxic Pollutants". Scientific American magazine. February 1998. Pages 86 -91.
  2. Wayne R. Ott ( Formerly of EPA and currently with environmental engineering department Stanford University. Co-author of Scientific American above.
  3. Ropeik, David and George Gray. Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You. Mariner Books; (October 28, 2002). ISBN: 0618143726.
  4. Wolverton, B.C. How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office. Penguin Books; (March 1, 1997). ISBN: 0140262431


Scorecard - The overall rating of an air-cleaning plant based on multiple factors. The higest rating is 10.

Transpiration - The natural process by which water evaporates from the plant. This will cool and circulate the air immediately around the plant, acting like a natural "air conditioner'. The higest rating is 10.

top of page | Home