Can indoor plants really improve indoor air quality?

A lot of indoor plant sellers will tell you that indoor plants will purify the air. Sometimes, they refer to experiments carried out by NASA to prove the point.  However, careful analysis of some of these claims shows that the claims are often exaggerated, or taken out of context.

That doesn’t mean that plants have no impact on indoor air quality – they can.  So, how can you get the most of plants’ abilities to affect the indoor environment? I can’t promise miracles, however.

A brief history

In the early 1980s, NASA was investigating the ways that astronauts could maintain their environments whilst on long-term missions.  The reaction of photosynthesis is a way of producing fresh oxygen for the astronauts to breathe, and some plants are good at removing other pollutants from the air and water.

The idea was that by having completely sealed living environments, coupled with optimal growing conditions for vast amounts of greenery, humans and plants could live in complete balance and the resources needed for a long-term mission could be reduced.  At the time, only a few years after the last manned landing on the moon and with early space stations (Skylab and Mir – the forerunners of the International Space Station) being lived in for months at a time, this research was clearly very important.

The results of the experiments showed that some plants were especially good at removing pollutants such as some volatile organic compounds (VOCs), some of which are quite unpleasant and are associated with harmful indoor air quality.  These have become quite well known and are often referred to as the NASA list of air cleaning plants.

Sick buildings – could plants be the answer?

In 1984, the World Health Organization gave a name to a recently discovered phenomenon.  People were feeling ill in modern buildings, and analysis of the environments in some of these buildings identified a number of VOCs as being likely causes of the problem.  That problem became known as Sick Building Syndrome, and a great deal of effort was expended trying to identify the building components most responsible for the release of these chemicals into the air inside buildings.

It didn’t take long for someone to notice that a lot of the VOCs identified as being associated with sick building syndrome were those that some plants seemed to be good at removing.  Indeed, one of the scientists involved with the original NASA experiments – Bill Wolverton – has since made a career writing about how houseplants can create fresh air.

However…

Thinking back to the original NASA experiments, you will notice that they were carried out with a specific purpose in mind, and the plants were grown under conditions that made them actively grow – their metabolism was optimized by controlling the environment with high light levels, good humidity, warm temperatures and precise levels of plant nutrients.  There were also vast numbers of plants in the growth chambers.

If you ever visit the hot houses at a botanic garden, such as Kew or the Eden Project, you will experience exactly the type of environment the plants experienced in the NASA experiments.  The air inside those spaces is uplifting, fresh and life-supporting.  The difficulty lies in recreating those conditions in homes and offices.

Issues of indoor air quality

Fortunately, since the early 1980s, the use of products in buildings associated with sick building syndrome has been significantly reduced.  Most homes and offices are not full of nasty VOCs.  However, there are some pollutants that have the potential to cause harm, or at least discomfort. 

Volatile organic compounds (VOCs)

There are many sources of VOCs in houses. In fact, almost everything you can smell is a VOC of one type or another. Paints and new furnishings often release some compounds, but more mundane products are the biggest source: cleaning products, cosmetics and toiletries. Cooking, too, also produces types of VOC, as does opening a bottle of wine or mixing a cocktail. Most of these VOCs are harmless, although some can be irritating.  Other VOCs are actually the result of human physiology: when you breathe out, there will be some VOCs on your breath as well as carbon dioxide and water – these are just the products of digestion and metabolism.

More worryingly are the VOCs that can enter the house from outside. Vehicle emissions, agricultural and industrial activities all contribute to VOCs in the atmosphere that will find their way indoors.

Fine particulates

A more pernicious threat to human health comes from ultra-fine particulate matter, usually produced as a result of combustion.  These are often classified as PM10 (particles smaller than 10 μm in diameter) and PM2.5 (particles smaller than 2.5 μm in diameter).  These particles can be breathed deeply into the respiratory system, where they remain.  Fine particulates come from vehicle exhausts, inefficient combustion of gases and even cooking.

Dust

Larger particulates, such as dust, can irritate the respiratory system and contribute to asthma and allergies.  These are either produced inside buildings (and are usually composed of dead skin cells and pet dander), or can be blown indoors through doors and windows (such as fine dust from roads and fields or construction, or pollen from trees and grass).  Since most homes are not airtight (and most people wouldn’t want them to be – opening a window is a great way to refresh the air and create cooling breezes indoors), there is little that can be done to prevent dust from getting in from the outdoors.  Remember, also, that good ventilation is recommended as a way of reducing the risk of Covid.

Carbon dioxide

Elevated levels of carbon dioxide are more of a problem in offices than in homes. Small meeting rooms with lots of people, will result in CO2 levels rising fast and getting to concentrations high enough to cause drowsiness and impair cognitive function.  In the home, this is less of a problem, although in the winter, when everyone is indoors and windows remain firmly shut, CO2 levels might rise above comfortable levels.

How can plants help

Despite the fact that most homes are unable to house enough houseplants to actively purify the air, nor are they able to provide the conditions for them to be physiologically active enough to achieve the sorts of effects seen under laboratory conditions (that would be extremely uncomfortable for people), there are ways that plants can be used indoors to improve air quality – and some plants are better than others.  

The key is to match the plants well to their environment.  The more closely matched they are, the more physiologically active they will be, and that is when the effects will be greatest.

When you search for indoor plants online (whether for home or office), you will often see that retailers often include details about the conditions that they do best under.  If you choose plants that suit the different conditions found in the various spaces in your home or office, then you are more likely to notice an effect.

Plants affect the indoor environment in three main ways.

First, the bacteria in the soil that live amongst the roots are able to break down some VOCs, and convert them into substances useful to the plants.  This is an entirely natural phenomenon, although only relatively recently properly understood in horticulture.  Plants with healthy roots and good soil will have the biggest impact, and those that are the fastest growing will also be the most effective.

Second, plants that are actively photosynthesizing will be removing some carbon dioxide from the air. Plants that originate in dark tropical conditions (such as rainforest floors) are able to photosynthesize extremely efficiently – they have evolved ways of making photosynthesis work even in very low light conditions, so that means more carbon dioxide is used by the plants.

Third, plants with hairy or slightly sticky leaves are able to trap particulates on the leaf surfaces, including fine particulates.  In fact, plants such as ivy and Cotoneaster are used outdoors to mitigate the effects of pollution in urban areas.  Some indoor plants can do that too (although they will need to be cleaned – there is no rain indoors to wash that pollution away).  In fact, research carried out at Washington State University some years back showed that many different types of foliage plant attracted dust to their leaf surfaces – possibly as a result of an electrostatic effect – so almost any leafy plant will be useful.

Which plants work best

Plants that are adapted to low light conditions will be the best to improve indoor air quality, especially reducing VOCs and carbon dioxide.  Plants in the aroid family, such as Spathiphyllum, Philodendron species, Aglaonema species or Monstera species will be good, as will other jungle-floor plants such as Calathea species, Ctenanthe and even small palms, such as Dypsis lutescens.

If light levels are slightly higher, Dracaena species have been shown to be effective at reducing levels of carbon dioxide (experiments carried out in Australia by Margaret Burchett, Fraser Torpy and colleagues, in real office conditions have shown that relatively few plants are needed to have a measurable effect).

Plants such as Ficus benjamina and varieties of ivy (Hedera helix) and some ferns that do well indoors are good at removing particulates.

Technological solutions

Over recent years, the plant/microbe interactions in the soil have led to a number of innovations that use plants to actively clean the air.  These systems were originally designed for large commercial spaces, but domestic-scale systems are becoming available.

In commercial buildings, green walls can have a dramatic effect on indoor air quality – especially when set up with good lighting systems. 

In the home, small green walls can now be purchased for relatively low cost, and can be installed by a competent DIYer.  Not only do they take up little in the way of floor space, the large volume of compact plants in a good root environment means that they are going to be very effective – especially if you invest in some plant lights to illuminate them (and these are also getting much cheaper).

More recently, active air systems have been developed that use fans to pass air through the foliage and the roots to increase the size of the effect.  Domestic-scale active air green walls are being developed and table-top systems, such as Vitesy’s Natede planter, are now already on the market.

disclosure note: the author has commercial relationships with foli8 and Vitesy

The biophilic home office

Image by Simply-C-Photography for Fusion Spaces

Biophilic design need not be confined to office buildings and other commercial spaces. The benefits of biophilic design can be obtained in the home office too, and without having to spend a fortune. My recent post for Fusion Spaces explores the benefits of biophilic design and gives some very simple and cost-effective tips to help you thrive in your home working setting – it’s not just about plants (although, of course, they are very important), it is about all of your senses.

Where we work now

Here in the UK, it is the last day of National Plants at Work Week, organized by the interior landscaping trade association, Plants at Work. Usually, this is a celebration of the benefits of greenery in the office.

This year, however, our workplaces are very different, and may continue to be for a while yet, and Plants at Work have been discussing the ways by which we can all use plants wherever we work – the home office, kitchen table, spare room or even in the garden.

Where we work is not just a room, with a desk and computer. For many, the place where we really work often isn’t physical at all, but inside our heads. The office and the laptop are just tools to communicate the outputs of work. For many, work can’t be measured by keystrokes or attentiveness to a camera or attendance at virtual meetings. At best, that is just a measure of activity.

Certainly, for some jobs, activity measures are the only practical proxy of work outputs, but those for whom the office is primarily the place to transfer ideas to a document or communicate them to a colleague, then the place where those ideas are formed is the real workplace. That means being in environments that forge creativity.

That could be a warm bath, or a walk in the woods. It could be the laptop on the dining table, but it may also be somewhere else entirely. Inspiration can happen anywhere and at any time – not just between 9 and 5 in an office block.

As good a place to be creative as anywhere. Photo by Tanner Vote on Pexels.com

For many years, those that have worked from home as a matter of course were often viewed with suspicion by employers and colleagues alike. Were they really working, or were they slacking off? (Were those employers incapable of actually measuring outputs?)

Some employers did insist on monitoring remote staff using technology, but now that even those managers are forced to working at home, maybe there is a little more understanding that people can be trusted to do good work without the need for a desk in the corporate office.

Evolution

It may be that as we contemplate the future of work, there will be a more rapid evolution of the home working environment. Already, employers, faced with a future when more and more people will be working away from the corporate office for extended periods, are examining their responsibilities for creating safe and healthy working environments.

This certainly includes getting technology right, and ergonomics. Good chairs and lighting are going to be vital, along with legal obligations such as complying with display screen regulations.

As well as the bare minimum, enlightened employers might be considering providing some of the things that make office life more bearable – perhaps some professionally prepared plant displays (e.g. this service from a London firm, Indoor Garden Design through their new venture https://www.intrayplants.com/ ).

Photo by Min An on Pexels.com

Some are even offering the delivery of home office buildings, although that raises many questions.

I wonder about how insecure a company must feel that it needs to remind its employees who they work for with a branded pod placed, presumably rent-free, in the back garden with the desk facing away from the window – recreating the environment of the office battery cage. If company culture has to be reinforced by having a massive logo, rather than by decent management, then I would be very worried. And what might be the consequence of hanging a poster over the logo?

The pod itself looks really well designed – good acoustics, modern lighting and all pre-cabled, but is this where you will be expected to be creative and imaginative? Maybe a few pot plants would help.

The nature of work is changing, and it is changing in ways not even imagined at the beginning of the year. Many office workers have had nightmares of trying to juggle space, homes schooling and caring along with work, but many have also experienced the benefits of being able to manage their work with more freedom, and have found themselves more productive, more creative and more engaged.

By being forced to loosen the leash on staff, employers should be seeing the benefits of empowerment and trust. The benefits to employers and employees of being liberated from the constraints of the workplace battery farm need to be preserved.

Post pandemic plantscaping

The workplace is no-longer the traditional office for many.  Many organizations are challenged by the need to embrace new ways of physically working: planning space, maintaining higher standards of hygiene, enabling teams to work effectively together and recognizing that home working is going to be needed (and even wanted) for the foreseeable future.  All of those challenges are overlaid with the absolute need to ensure the physical and mental wellbeing of staff.

As we move through summer, many offices and other workplaces are re-opening and businesses are trying to imagine how on Earth they are going to be able to ensure effective working.  This uncertainty and the requirements for correct physical distancing and enhanced hygiene standards is going to place a strain on employers and employees alike. 

We’re beginning to get some hints about the way things might look in the period immediately after lockdown ends. One thing is for sure, the world of work (especially the office) is going to have to adapt very quickly. Even when buildings reopen, it seems likely that some degree of physical distancing and enhanced hygiene will be necessary.

After the second world war, a great leader found himself ruthlessly put out of power.  Churchill led the country through a crisis and might have expected a reward in the subsequent general election.  However, to his surprise, and that of the press and the establishment, he fell victim to the closest thing the UK ever had to a revolution.

Comparing the horrors of global warfare to the enforced changes to office life is a bit extreme, although it is worth drawing a few parallels.

Wartime highlighted the faultlines in society.  The old order had to be abandoned in order to fight the war and the idea that society would willingly return to the established ways of doing things was rejected.  Now, organizations are going to have to face up to the facts that the established ways of managing people and workspaces are also going to have to change.

We may even have to reconsider what we mean by workspaces.  

It is going to be a long time before this is normal again, if ever
Photo by fauxels on Pexels.com

Do we mean just the one (or more) physical spaces to carry out work – the realm of the designer – or does it include the headspace too?

Opportunities

Workplace managers are going to have to consider whole new interactions of disciplines in the very near future: space, furniture, technology, connectivity, restoration and recuperation, and new approaches to managing people.  All will need repackaging to create work environments that people want to use, and we must learn from our experiences over the last few months to create those new working environments.

What does that mean for the commercial interior and exterior plantscaping industry?

There are certainly going to be challenges, but also opportunities for those firms imaginative and agile enough to change.

Let’s first look at some of the challenges. These include adapting to new ways of working, such as maintaining physical distancing in clients’ offices whilst carrying out plant care, ensuring that plant displays are kept clean and disinfected and adapting to new office layouts that might be less accommodating for plants if desks and workstations have to be spread out.

One thing seems certain: high density offices are going to have to change. If physical distancing is going to be successful, then either desks are going to have to be spread out, or there are going to have to be screens between workstations, or fewer people are going to be allowed in the office at any one time. Pedestrian routes will also have to be altered. It will be no good if desks are isolated only for colleagues to have to squeeze behind the back of your chair or walk within a few inches of you as they go and get their coffee.

Graphic by Plants@Work – the UK trade association for interior landscapers

Already, interior designers and architects are producing their visions of the new normal office. Many solutions seem to revolve around an adaptation of conventional open plan spaces with designated empty desks and plastic screens to facilitate physical isolation. Some designers are a little more imaginative than others and have started investigating how people can be safely separated with items such as plant displays and green dividers comprising of moss, live plants or even replica foliage. These are, on the face of it, attractive options.

The most imaginative of all are re-thinking the way that offices are going to work. After months of homeworking, most people have found that they can do their work pretty well from home, or at least can manage without missing the office too much. Work habits have changed and people are finding ways to adapt to remote working. The traditional corporate office environment has been shown, by and large, to be unnecessary.

Those organizations with the imagination to grasp the opportunity to create better office environments, rather than rush to adapting what already exists, may look to the types of environment typified by co-working spaces and serviced offices. Such places often resemble hotel lobbies and coffee shops, but also with a wide variety of working spaces to accommodate any type of activity. Such places are designed to get specific types of work done, rather than be a place to go to work.

The new office might be fitted out with better furniture, art and plants. They won’t be designed for dense occupation, but will enable physical distancing, and they will be adaptable to a time when such extreme distancing is no-longer needed.

In part two of this article, I’m going to look at some practical considerations for plantscapers. But if you can’t wait, do get in touch and we can talk about some ideas.