How to improve indoor air quality

The need to measure indoor air quality

The question of how to improve indoor air quality must be preceded by the question of why we need to improve it in the first place. Only once we address why we need to improve indoor air quality (IAQ) are we confronted by the problem of monitoring and measuring it.

In January 2024, Dyson revealed the results of its first Global Connected Air Quality study. Using IAQ data from over 2.5 million of its air purifiers, the study found that from 2022 to 2023, indoor air quality was worse than outdoor or ambient air quality for 11 months of the year, especially in the United Kingdom. As for other countries from where data was collected – in 85% of countries (that is all but four countries), PM2.5 levels indoors exceeded those outdoors for 6 months at the very least. Additionally, in regions with harsh winters, people tend to spend more time indoors during this season, with Dyson’s data revealing that this season was the most polluted globally; closed windows, candles lit indoors, and heating systems are likely the sources of this indoor pollution. While this study was largely UK-focused, the same trend remains the world over: indoor air is often more polluted than outdoor air, and our homes and offices are far more polluted than most people believe.

How to improve air quality at home? First, examine the products you’re using.

A couple of years ago, a story in New Scientist highlighted a study claiming that cleaning products cause indoor pollution levels comparable to a busy road. Very often, scented surface cleaners contain citrus- or pine-scented chemicals called monoterpenes. When these monoterpenes evaporate (which happens quite easily), they react with unstable molecules like ozone in the air to produce pollutants known as secondary organic aerosols (SOAs). Vehicle fumes also generate SOAs, with the study claiming that using monoterpene-containing products indoors can expose you to a similar amount of pollutant particles as a road used by 28,000 vehicles a day. While the precise health effects of SOAs with indoor sources are still unknown, if they are even a little bit as toxic as vehicular emissions, we have serious cause for concern.

Regardless, SOAs are only one of many, many causes for concern when it comes to the quality of indoor air. In an overview of indoor air quality design tools for schools, the United States of America’s Environmental Protection Agency (EPA) listed the typical sources of indoor air pollutants. Want to know how to improve indoor air quality? You’re going to have to worry about more than just SOAs.

Polluted outdoor air, which makes its way indoors through doors, windows, cracks, and joints in building design, fills indoor air with pollen, dust, mould spores, vehicular emissions, industrial emissions, and other engine emissions. The concentrations of these and other pollutants are heightened by close proximity of outdoor air intakes to loading docks, dumpsters, unsanitary debris, or building exhausts. What’s more, underground sources like radon, pesticides, and leakages from underground storage tanks also present threats to indoor air quality and, consequently, to human health.

If you feel like you now know all you need to know as to how to improve air quality at home, we hate to break it to you, but there are several indoor sources you need to worry about as well. When installing or replacing building equipment, take special note of HVAC equipment. HVAC equipment could be a source of mould growth in drip pans, coils, ductwork, and humidifiers. Further, dust or debris in ducts, or improperly vented combustion products could also make HVAC equipment hazardous to your health and well-being. In terms of other equipment, office machines like printers etc. and shop, laboratory, and cleaning equipment could release ozone, volatile organic compounds (VOCs), and other hazardous gaseous pollutants.

Water-damaged materials in your home or office could house mould growth. Dry drain traps could allow the passage of sewer gas. Asbestos used to make and furnish the house could break down and pollute the air. New furnishings and floorings could emit noxious gases. Candles, art supplies, cooking, smoking, markers, incense, and personal care products are also sources of indoor pollutants.

This list is long, but hardly exhaustive. The answer to how to measure indoor air quality and improve it? First, control as many of these sources as possible. For instance, you could avoid burning incense indoors, or switch to personal care products which don’t emit VOCs. We will dive deeper into the topics of source control and how to improve air quality at home in later parts of this article.

Okay, that’s a lot of pollutants. So what?

Indoor air pollutants include particulate matter (PM2.5, PM10 etc.), nitrogen dioxide, nitrous oxide, sulphur dioxide, carbon dioxide, carbon monoxide, VOCs, ozone, and other particulate and gaseous substances. So what?

In outdoor settings, these pollutants have adverse impacts on both human and environmental health, with climate change only making matters worse. In indoor settings, they have a more pronounced effect on human health, considering we spend so much of our time inside our homes, offices, or other enclosed spaces.

Particulate matter can penetrate into our respiratory systems to trigger or worsen conditions like bronchitis, asthma, chronic obstructive pulmonary disease (COPD), and allergies to dust mites, pollen, or other airborne substances. Particulate matter has also been associated with heart attacks, cardiovascular diseases, and premature deaths.

When oxides of nitrogen react with VOCs in the presence of sunlight, ground-level ozone is produced, which contributes to lung irritation and also more severe respiratory issues, especially in children, older adults, and people who already have other health concerns.

Overall, indoor air pollutants have been associated with irritation of the eyes, throat, and nose, skin rashes, headaches, fatigue, and dizziness. They have been associated with low birth weights, cognitive impairment, increased cancer risk (especially lung cancer), stroke, and ischaemic heart disease. Addressing the root cause of these health issues always comes down to how to improve indoor air quality.

So the question isn’t to improve IAQ or not to improve IAQ. The better questions are how to measure indoor air quality; how to improve indoor air quality; and how to ensure that with each breath we take, we are nourishing our bodies rather than harming them.

How to improve air quality at home

To improve anything, we need to measure it. Real-time air quality monitoring is absolutely essential to assess pollution sources, trends, and the impact of mitigation measures. In recent years, advances in sensor tech and data analytics have led to the industry developing smart air quality monitoring systems. These systems are indispensable when it comes to maintaining a safe indoor environment; they can be relied on for accurate data, which can help you take action to improve IAQ in your home immediately and in the long term.

How to measure indoor air quality

Okay, so now you know what we’re dealing with overall in terms of indoor air pollution. You still have to make a more specific assessment of your own surroundings. If how to improve indoor air quality is the question on your mind, your first step to answering that should be identifying the sources of indoor pollution in your immediate environment.

You’re possibly experiencing an allergic reaction or respiratory distress, and you suspect that it’s the factory in the neighbourhood, which has been emitting clouds of smoke, which is to blame. Or maybe your kitchen or your bathroom isn’t ventilated enough to let some fresh outdoor air in. Or possibly, your building was constructed several years ago and hasn’t been well-maintained – it’s possible you have mould growth from water damage, or disintegrating asbestos hidden away from view.

When you ask how to improve air quality at home, you’re opening a whole can of worms, addressing which may require improvements to your building design, HVAC system, and/or changes in the kinds of personal care products you use. But as you can tell from the aforementioned health effects of poor indoor air, it will be a worthwhile can of worms.

Investments and research on how to measure indoor air quality

While outdoor air pollution has for long basked in the spotlight, historically, its indoor counterpart hasn’t received as much attention. Thankfully, that’s changing quite a bit. This is reflected not only in the proliferation of indoor air purifiers in the market but also in government funding priorities.

A market report by Mordor Intelligence has suggested that the combined market for both indoor and outdoor air quality monitors will grow at a CAGR of 5.79%, from a value of US$ 5.08 billion in 2024 to US$ 6.73 billion in 2029. Though fragmented, the industry boasts several players like Siemens AG, Thermo Fisher, Honeywell, and other manufacturers and suppliers who have dipped their toes in outdoor and indoor air quality monitoring.

The indoor air quality monitor market is vast and diverse. It is segmented by sampling method, end-user applications, and type of sensor.

Sampling method: Continuous or intermittent; manual or automatic
Applications: Residential, commercial, or industrial
Sensor type(s) or air quality measurement parameters: Particulate matter (PM), carbon monoxide, volatile organic compounds (VOCs), moisture etc.

Despite being a fairly established industry, research and innovation on how to improve indoor air quality by accurately measuring it is far from stagnant; as we’ve mentioned, it has also been a funding priority for some governments. For instance, for the years from 2019 to 2025, the UK government invested a sum of £42.5 million in the Clean Air programme, to explore the health impacts of poor air quality by funding cutting-edge interdisciplinary research. Under this programme’s Strategic Priorities Fund, Innovate UK also launched a competition, funding a bunch of pilots focused on new air monitoring technologies for domestic environments. Innovations resulting from funded projects have helped households to accurately identify common pollutants in their homes, pinpoint their sources, receive alerts when certain thresholds are crossed, and find actionable suggestions on how to improve air quality at home. Mobile apps, AI prediction models, and interactive human-centred design are all part of the future of indoor air quality monitoring.

What will work best for you?

Ultimately, for individuals, households, employers, business owners, building managers, and anyone else interested in how to measure indoor air quality, a continuous air quality monitoring device is the solution. Of course, that’s not the end of the answer. Once you decide to invest in an indoor air quality monitor, you have to think about which specific monitor to purchase. Across the many offerings available in the market, specifications vary widely. But there are certain non-negotiables that we suggest you never compromise on when making a purchase. Here’s our list:

1. Continuous, real-time monitoring
   
   Indoor air quality doesn’t remain constant throughout the day, month, or year. There may be spikes in certain pollutants when you’re cooking or when you’re dusting the house. Wildfires may bring certain pollutants into your home or office only when, well, there’s a wildfire raging in the region. Wintertime, peak traffic time, or the bursting of firecrackers may all contribute to the air quality within the home and other enclosed spaces you occupy.
   
   To take immediate action in emergency situations, like when the threat of carbon monoxide poisoning emerges, your monitor should give you real-time updates. Otherwise, the data from your monitor may be too little too late. The damage from acute pollutant exposure would already have been done.
   
   
2. Accuracy
   
   Whether indoor air quality changes around you are rapid or sustained, the need for accurate monitoring data need not be explained. The accuracy test data of the sensors in an air quality monitor can be obtained from the product manufacturer, the sensor supplier, or independent third-party testers. For an IAQ monitor to be considered a good one, accuracy should fall within the following minimum brackets: ± 10-20% for PM levels; ± 25% for tVOC, ±5% for CO2, ± 3% for relative humidity, and ± 1 mBar for air pressure.
   
   
3. Sensor type(s)
   
   All air quality monitors don’t measure all air quality parameters. What a particular device can measure depends on the type(s) of sensor(s) it is fitted with. IAQ monitoring devices may be designed to measure some or all of the following pollutants: carbon dioxide, volatile organic compounds (VOCs), radon, particulate matter (PM), carbon monoxide, humidity, and/or temperature. After an initial assessment of the potential sources of indoor air pollution in your home, you may have an idea of what kinds of sensors are most apt for your surroundings. For instance, cigarette smoking is a source of PM2.5 and VOCs. But for general use cases, monitors with sensors for the greatest number of air quality parameters are preferable. However, never compromise on accuracy for the sake of more types of sensors.
   
   
4. Sensor calibration
   
   Many people, when they invest in an indoor air quality monitoring device, do not realise that there is a recurring cost and effort involved: that of sensor calibration. With use, sensors begin to stray from accuracy; this is a natural and expected part of air quality monitoring. Regular calibration is necessary; you can achieve this either by buying a device with auto-calibration features or by sending the monitor to a technician who can manually do the job for you. While the latter is preferred, it is characterised by some logistical challenges. Avoiding those logistical challenges is possible with Kaiterra’s technology, which allows you to simply remove and replace degrading sensors.

In subsequent parts of this article, we’ll tell you more about how to improve indoor air quality and the larger forces at play in policy and industry, which are making sure that the onus of managing indoor air quality does not fall on individuals and households alone.

10 actionable tips to improve indoor air quality

Now that we’ve talked about the numerous pollutants – particulate matter (PM), radon, formaldehyde, other volatile organic compounds (VOCs), oxides of nitrogen, ozone, carbon dioxide, carbon monoxide…. the list goes on – with whom you’ve unknowingly been sharing your home, and how to measure indoor air quality, let’s get to what you can do about it.

Taking things into your own hands: How to improve air quality at home and in your workplace

Considering the massive number of industrial and vehicular contributors to outdoor air pollution, fixing the problem of ambient air quality is beyond the circle of influence of most individuals. Thankfully, as individuals, we can do much more to control our exposure to indoor air pollutants, even though they are fairly interlinked with outdoor pollutant concentrations.

Trusted organisations like the United States of America’s Environmental Protection Agency (EPA) recommend a three-step method for how to improve indoor air quality. Source control, ventilation, and air cleaning.

Source control: This involves identifying the products and activities which are generating hazardous air pollutants and nipping the problem in the bud. This could involve avoiding burning incense or scented candles indoors, not smoking indoors, using personal care and cleaning products which don’t contain monoterpenes and don’t release VOCs into the air, and not smoking in enclosed spaces. However, even when some sources are accurately identified, completely eliminating their use can be difficult. For instance, certain office equipment like printers can emit polluting gases into the air, but not using a printer at all may not be an option. This problem can be circumvented by trying to minimise people’s exposure to the generated pollutants – offices could, for example, place the printer in a location far away from where employees spend long hours working.

Ventilation: When source control is not an option (and even when it is), ventilation is crucial. Ventilation allows polluted indoor air to be diluted by fresh outdoor air that is circulated into an enclosed space. It is a good practice to open windows and/or doors for at least 15 minutes daily to air out closed spaces. Further, ventilation is necessary during cooking or hot showers; outward-ventilated exhaust fans fitted in kitchens and bathrooms, when used appropriately, can help eliminate harmful fumes from your home. Again, of course, ventilation is not always possible. For example, if you live close to a factory or construction site, letting unfiltered outdoor air into your home or office could make the air quality indoors worse. This is where appropriate HVAC systems and other interventions mentioned below might be more useful.

Air cleaning: Prevention and management is better than cure. But when source control and ventilation do not give you the pristine indoor air that you would like to breathe, the question of how to improve indoor air quality persists. As a last resort, we come to air cleaning. There are many ways in which you can clean indoor air, some more simple than others. The most straightforward and commonly used mechanism nowadays is to invest in an air purifier.

How to improve air quality at home and at work: 10 actionable tips

There are many actionable tips that you can take yourself. Each of these complements the above general principles of source control-ventilation-cleaning, setting you on a path to address how to improve indoor air quality.

1. Dust, vacuum, and/or mop your space regularly. Pollutants generated from outdoor sources, including wildfires, can enter and remain inside your home or office for weeks on end. Simple measures like dusting, vacuuming, and mopping regularly can help you to lower not only the levels of VOCs and PM in the air but also those that have settled on indoor surfaces like window sills, sofas, tables, floors, doors, etc. and are re-emitted into the air over time.
   
   
2. Use non-polluting cleaning products. Most conventional surface cleaning products contain monoterpenes or other VOC-releasing compounds. Excessive use of these products indoors can lead to pollutant buildup indoors. So, instead, you could switch to green cleaners, which are made using natural ingredients like baking soda, citrus fruit, white vinegar, borax, or essential oils. These are safe and effective alternatives to harmful chemical products.
   
   
3. Invest in some indoor plants. Who doesn’t love a clean, green room filled with natural beauty? Plants like English ivy, bamboo palms, peace lilies, pothos plants and many others are extremely effective at removing different pollutants from the air. Even NASA vouches for this air-cleaning technique.
   
   
4. Make efficient use of entry mat barriers. Many pollutants enter buildings on people’s shoes. Stepping into your office building after being exposed to the elements outdoors, you may bring visible dust and dirt indoors, as well as invisible moisture and other pollutants. These are then spread across the floors and carpets that you traverse, making the indoor environment more hazardous and maintenance more tedious. Effective entry mat systems are a simple solution to minimise this problem, though your entry mat system should be designed for your particular climatic conditions. A scraper mat is best suited to snowy weather, an adsorption mat to a rainy climate, and a large number of different kinds of mats for a muddy location.
   
   
5. Install automatic drain trap primers. Most drain traps in sinks, bathrooms, etc., aren’t a hazard to IAQ because they are in continuous use. But when a drain trap is not used often, it dries out and allows sewer gases with components like hydrogen sulphide gas to enter the building and cause health risks. Installing automatic drain trap primers in all floor drains can ensure that they don’t dry out and spread noxious gases and odours to other parts of the building through the HVAC system.
   
   
6. Ensure sewer vents are not close to an outdoor air intake. When a sewer vent is too close to an outdoor air intake for an HVAC system, sewer gases can re-enter the building. This problem has a simple solution: extend or move the sewer vent to another location.
   
   
7. Use HEPA filters. Fairly common now in the post-Covid world, high-efficiency particulate air (HEPA) filters help reduce indoor air pollution. They eliminate pet dander, dust mites, mould spores, tobacco smoke, and other airborne pollutants. As their name suggests, they are particularly good at removing small particles from the air, even those that are as small as 0.3 microns. You can use a HEPA filter in your vacuum, air purifier, or HVAC system.
   
   
8. Use low-emitting furnishings and building materials. Wool carpets, latex paint, and bamboo are good alternatives to high-emitting furnishings. You can use materials such as these when you’re building or renovating your home, as they generate fewer VOCs and keep you safe from air pollutant-linked health complications.
   
   
9. Keep your home and office dry and clean. Moisture leads to mould and mildew growth, which is an indicator of poor indoor air quality. Eliminating moisture is the best way to eliminate these pollutants and the health issues that come with them. This step is particularly important in rooms like kitchens and bathrooms where moisture is most likely to be generated.
   
   
10. Use air purifiers. Air purifiers can help you to effectively tackle many different pollutants including carbon monoxide, VOCs, dust, PM, pet dander, and mould spores. What you should be sure to do is select a purifier which is the right size for your room. You can do this by checking its CADR, or clean air delivery rate. Divide the square footage of your room by 1.55 to get a figure, let’s say, x. The air purifier you buy should have a CADR of at least x if it’s to do its job effectively.

These simple steps can help you take your health into your own hands. By cleaning the air inside your home and office by yourself, you can be guaranteed that you are keeping yourself, your family, your employees, and your community safe from the hazardous effects of indoor air pollutants.

Nonetheless, the onus of cleaning up the air should not be yours alone. Clean air should be a free good; it should be abundant, shared by all, and the responsibility of all. In the next article in this series, we’ll explore research, policy, and corporate initiatives that listen to us as we #DemandHealthyAir.

How to improve air quality: A shared burden

The question of how to improve indoor air quality is deeply interlinked with outdoor air quality. Maintaining pristine air indoors is definitely important, but all your efforts to clean indoor air are futile if, when you step out, you’re breathing in excessive amounts of particulate matter, carbon dioxide, carbon monoxide, smoke, etc. Moreover, since there are multiple points where indoor air interacts with outdoor air, the former is hardly likely to remain clean when vehicles, industries, agricultural, or waste management systems consistently pollute ambient air. Our point here is that cleaning indoor air must go hand-in-hand with improving outdoor air quality.

This brings us to an important question: whose problem is overall air quality? On whom does the onus lie to make sure that not only our homes and offices but also our shared public spaces and community areas are safe, livable, and breathable?

Regulatory frameworks mandating minimum acceptable levels of indoor air quality (IAQ) don’t exist in India. Still, there are other laws and regulations which focus on different aspects of the safety of buildings, workplaces, and ambient air in general. Internationally, there are also standards and regulatory frameworks focused particularly on indoor air quality, outlined by authorities in other countries and by international organisations.

That’s not all. The problem of indoor and outdoor air quality has gained traction as a research priority for the past several years – one of the most notable examples is the UKRI’s Clean Air programme that we mentioned earlier. Researchers and research funders have prioritised the questions of how to measure indoor air quality, how to improve air quality at home and outdoors, and how to even gain economic value from air pollutants by turning them into useful products.

So, while the problem is dire, fortunately, organisations – governmental and otherwise – have stepped up to understand, assess, and mitigate it with policy and technology. In this final article of this series, let us explore some of the international standards, innovative technologies, and policy strategies being employed to reduce air pollution.

How to improve indoor air quality: International guidelines, standards, and regulations

International and national bodies around the world have issued guidelines and regulations to provide households and businesses with air quality standards that they should aspire to and work towards.

The World Health Organisation (WHO), as the specialised agency of the United Nations (UN) concerned with public health, issues global air quality guidelines, including indoor air quality guidelines related to household fuel combustion, particulate matter (PM2.5 and PM10), and other selected pollutants associated with poor IAQ, like carbon monoxide, benzene, formaldehyde, nitrogen dioxide, naphthalene, polycyclic aromatic hydrocarbons, radon, trichloroethylene, and tetrachloroethylene.

The international standard ISO 16814:2008 addresses IAQ in building design, offering methods to assess and indicate how suitable indoor air quality is for human occupancy.

CIBSE Guides, particularly KS17, provide guidelines concerning IAQ and ventilation, with international best practices on how to improve air quality.

The United States’ Environmental Protection Agency (EPA) does not regulate indoor air, but it does offer assistance to citizens in protecting their IAQ. The agency provides guidelines for cleaning mould and addressing moisture problems in schools and commercial buildings. Additionally, the country’s Clean Air Act (CAA) mandates that all major stationary sources of air pollution must obtain operating permits, install pollution control equipment, and meet certain emissions limitations. The CAA also requires the EPA to regulate emissions of toxic air pollutants from specified industrial sources, bringing mercury, benzene, polychlorinated biphenyls (PCBs), and volatile organic compounds (VOCs) under the purview of national regulations.

The US Occupational Safety and Health Administration (OSHA)’s purpose is to ensure safe working conditions. This encompasses workplace aspects related to indoor air quality.

The European Union has the Ambient Air Quality Directive as well as standards for particular indoor pollutants. Meanwhile, the United Kingdom has the Workplace Health, Safety, and Welfare Regulations, which require employers to guarantee sufficient ventilation in enclosed workspaces.

In India, Section 13 of the Factories Act, 1948, includes requirements related to ventilation. The Air (Prevention and Control of Pollution) Act, 1981, and the Environment (Protection) Act, 1986, govern ambient air quality, which is deeply interlinked with IAQ. The Bureau of Energy Efficiency’s code, under Comfort Systems, mandates mechanical or natural ventilation for buildings, while the Indian Green Building Council has formulated IAQ-associated standards and certifications.

How to improve air quality: Transforming pollutants

With an optimistic vision for the future of how to improve air quality, organisations like Graviky Labs have taken to converting air pollutants into useful products. Graviky uses the technique of carbon sequestration to store carbon from the atmosphere and process these collected emissions into usable carbon. This incredible process converts hazardous carbon pollution into inks, ethanol, liquors, plastics, and other useful everyday products.

But innovations such as this are not alone. Research in recent years has found that oxides of nitrogen, which are major pollutants with severe health impacts, can be transformed into not only harmless but possibly even useful nitrogen products. Notably, scientists have been attracted to the idea of reducing oxides of nitrogen to hydroxylamine, or NH2OH, which has applications in renewable energy.

Other technological innovations in this space include using nanotechnology to enhance the efficiency of electrostatic precipitators, which are used to remove particulate matter from industrial pollutants; photocatalytic coatings, which use sunlight or the heat from lamp lightbulbs to break down nitrogen oxides and VOCs in the air; biofiltration and bioremediation systems which use not only plants but also microorganisms to clean up the air naturally; and the electrochemical conversion of carbon dioxide, like the tech used by Graviky, to convert the gaseous pollutant into fuels, chemicals, and building materials.

Today, the problem of air pollution – both indoor and outdoor – does not exist in isolation. It influences and is influenced by the worsening climate crisis. Some of the major sources of air pollution, like industry, aviation, and motor vehicles, are also major contributors to the climate crisis; the combustion of fossil fuels releases pollutants and greenhouse gases, which trap more and more heat in our atmosphere. So, addressing the air pollution problem requires a response coordinated with climate action. The sheer scale of the air pollution-climate crisis nexus demands that governments, multilateral agencies, and large corporations get involved. The problems of how to measure indoor air quality and how to improve air quality at home shouldn’t be left to individuals and households alone. Regardless of the actions that we can take ourselves, it is high time that we hold those responsible for public health and safety responsible and #DemandHealthyAir.