Can House Plants Purify The Air In A Room?

So you’ve heard that houseplants can purify the air in your house.

Great news, right?

Well, this would be great if it were true, but the reality is a little more complicated than the sensationalist headlines suggest.

This article will try to separate the fact from fiction.

There is actually some evidence that house plants have a beneficial impact on the pollutant and oxygen levels in a sealed environment. The concentration of a small number of pollutants have been scientifically tested over the last 30 years to assess the impact of plants on the concentration of these hazardous chemicals.

However, this is unlikely to result in any real world benefit. This article will discuss why this is the case, and also discuss some actual benefits of having plants in your house.

What Are The Facts?

The quality of indoor air is increasingly recognised as an important factor in maintaining long-term health. There are many factors that can influence the quality of indoor air such as the concentration of volatile organic compounds, temperature and humidity.

In particular, volatile organic compounds can have a negative impact on human health over time. There have been a number of studies which have looked at the concentration of volatile organic compounds in indoor areas.

A study published in the journal “Indoor Air” in 2011 looked at the concentration of chemical air contaminants in a number of residential properties and found that 18 of the 59 VOCs measured were higher than at least one of the recommended guideline values.

This is a worrying fact.

Volatile organic compounds are released from a number of  interior furnishings such as carpets, sofas and electric equipment. There are a number of things that you can do to reduce the volatile organic compound concentration in your home, such as buying products with low emissions and ensuring that your home is well ventilated.

Using plants as a way to reduce VOCs in indoor environments is something that has been looked at in over 44 published studies. The first published study from NASA, by Wolverton et al, led to considerable publicity and triggered considerable further research into this area.

Nasa Study

Researchers at NASA were able to show that a plant grown in soil, in a closed environment led to a reduced level of benzene, trichloroethylene and formaldehyde in the surrounding air. However, when the leaves of the plant were removed, there was a very similar reduction in the concentration of these chemicals.

When soil alone was used, there was a small reduction in the concentration of benzene, trichloroethylene and formaldehyde. The results of this study would suggest that the roots and microorganisms within the soil, rather than the foliage, are responsible for the greatest effect on VOC concentrations.

This initial research led to considerable further research to expand on these early findings. However, the list of VOCs that have been tested remains very small, so this significantly limits the value of these studies in answering whether a long list of non-tested VOCs are impacted by the presence of plants.

The mechanism by which plants remove VOCs from the air can be broken down into four mechanisms.

1. Removal by the above ground plant part.
2. Removal by the microorganisms residing in the soil
3. Removal by the roots
4. Removal by the growing media

There is still considerable uncertainty about the relative importance of each mechanism.

The Bottom Line

Most of the studies so far have shown that plants can purify air to an extent by reducing the concentration of a number of volatile organic compounds in the air. However, the rate at which they do this is completely insufficient to make any meaningful difference on the air quality in an inside space.  

Why Will Plants Not Make Much Difference To Air Quality?

There are two very good reasons why these study results are not applicable to the real world.

The first is that for most of the studies, the volume of plants and soil relative to the air volume was much higher than would be practical for most people to achieve at home. It has been estimated that you would need to have a house plant for every 100 square feet in your house to replicate NASA’s results in an airtight building.

The second and most important factor, however, is that the air in your house changes many times per day. The entire volume of air in the average home in the United States changes every 30 to 60 minutes, meaning that any benefit that plants bring to pollutant levels is immediately lost as the air within a room changes and is replaced by air from outside.

How Can You Make Sure The Air In Your House Is As Clean As Possible?

OK, so plants aren’t really going to make the air in my house any cleaner, but what can you do?

For the vast majority of homes, the air outside will be significantly less polluted than the air inside. This is due to the number of furnishings within the average home which emit volatile chemicals which negatively impact air quality.

One of the simplest things you can do is increase the ventilation in your house.

Seems a bit too simple, I know.

However, opening your windows and increasing the rate at which the air changes in your house can significantly improve the air quality inside. This can actually improve your health over the long term.

Fair enough, if you live in a very cold climate you may not be so keen to open all your windows, but it is worth bearing in mind.

Home ventilation rates are significantly lower in winter, as many of us close our doors and windows and put the central heating on. It may be worth putting an extra layer of clothing on and opening a window from time to time, if it is going to have a positive impact on your health.

Clean House = Clean Air

Many of the pollutants in the air inside your home originate from your furnishings. Whether is is carpets, mattresses or curtains, many materials will release potentially harmful volatile chemicals that can cause harm to your health over time.

Equally, when you walk into your house, you are bringing dirt and pollutants inside on your shoes. By leaving your shoes at the door and regularly cleaning soft furnishings and floors, you can significantly reduce the pollutants within your home.

Reduce Humidity

Humid environments are a breeding ground for mould, which can be particularly hazardous to health. Mould spores readily become airborne and can cause direct allergic effects on your airways and skin. Fixing leaks, ensuring good ventilation and considering a dehumidifier if required, are good ways to reduce the impact of mould.

Eliminate Smoke From Inside

Second hand cigarette smoke contains thousands of hazardous volatile chemicals. If there is a smoker in your house, the biggest improvement to indoor air quality will come from getting them to smoke outside.

It’s not just smokers that can impact air quality. If you have an open fire, the volatile chemicals that are emitted from the fire can have a very serious, negative impact on your health. You could consider heating your home by an alternate method or consider installation of an enclosed gas fire.

For more information on how to improve indoor air quality, check out this great article.

What Are The Benefits Of Indoor Plants?

So, if plants aren’t going to make the air in my house cleaner, do they have any real health benefits?

Plants can fight colds and sore throats

Believe it or not indoor plants can actually reduce your risk of getting coughs colds and sore throats and improve your energy levels. There's actually been a number of studies that have measured the effect of plants on improving your health.

One study in the United States compared surgical patients who had plants in there rooms vs patients who did not have plants in their rooms. Surprisingly, the patients who had plants in their rooms recovered quicker and required less pain relief than those patients who did not have plants in their rooms.

A number of studies have looked at workplaces, and have found that the rate of sick leave decreases in offices where plants are present. Another study found that the incidence of symptoms such as coughs, colds, dry skin and headaches also decreased in workplaces where plants are present.

Plants Reduce Noise

Plants have a great role in reducing indoor noise as they are natural sound absorbers. if your home has a lot of hard surfaces, plants can be used to soften the environment and create a more pleasant acoustic environment. this will in turn lead to decreased stress levels due to the more pleasant auditory environment.

Plants Can Make You Happy

There are so many aspects of having plants in your house that can improve  your sense of wellbeing. they're appearance and smell are pleasing and the satisfaction that we gain from looking after a living thing can add to our level of happiness.

Believe it or not, people who have plants in there home tend to have lower blood pressure than those who don't. the mechanism for this is unclear, but I certainly find that having indoor plants brings me a lot of happiness and reduces my stress levels which have no doubt is part of the reason why this happens.

Plants Help Adjust Humidity Levels

Plants are responsible for a significant proportion of the humidification of the air around us.

In an enclosed space inside your home, they play an even more crucial role. It isn't healthy or comfortable to be an environment that is either too humid or to arid.

It is generally recommended to try and keep your living environment at a relative humidity level of between 40 and 60%. If you live in a particularly arid location, plants can be used to naturally increase the humidity of your indoor environment and increase your comfort and health.

Increased Concentration

It is likely that as a consequence of their positive impact on mental health, and that plants can increase your concentration levels. adding a few plants to your indoor space may help you to concentrate harder or to be more productive.