A Primer on Indoor Air Quality (IAQ) Monitoring Techniques

A Primer on Indoor Air Quality (IAQ) Monitoring Techniques

Introduction: What is Indoor Air Quality?

Indoor Air Quality (IAQ) refers to the air quality within buildings or enclosed spaces where people live, work, or spend significant time. Indoor Air Quality (IAQ) is more than just a buzzword; it is a vital component of the spaces where we live, work, and play. Far from being just “air,” IAQ encapsulates the broader ecosystem of Indoor Environmental Quality (IEQ), a matrix that also includes lighting, temperature, and acoustics. From hi-tech computer simulations to old-school surface studies, indoor air quality monitoring techniques are a complex affair that examine variables like temperature, humidity, carbon dioxide levels, fine particles (PM 2.5), air pressure, and Volatile Organic Compounds (VOCs).

The Life-and-Death Importance of Monitoring IAQ

If you think IAQ is just about comfort, think again. According to the World Health Organization, poor IAQ was linked to a staggering 3.2 million deaths globally in 2020 —237,000 of these were children under five.

Poor indoor quality has numerous harmful effects on human health. Symptoms from short-term exposure to spaces with poor IAQ include irritation of the eyes, nose, and throat, fatigue, and headaches. Long-term exposure heightens risks of cancer, heart disease, and severe respiratory issues. Some VOCs can even harm the liver, kidney and central nervous system.

Recent research has also revealed an undeniable link between poor indoor air quality and its worrying impact on psychological health. These include increased stress levels, irritability, and even symptoms of anxiety and depression. Poor IAQ also affects cognitive functions like memory, attention, and decision-making abilities.

Developed countries have started to catch on, incorporating IAQ measures into building design, but many emerging economies are still lagging behind.

The Usual Suspects: Factors Influencing IAQ

IAQ is the outcome of a wide and diverse range of factors. While some may be obvious, others might be hiding in plain sight.

Indoor Pollutants: Not as Friendly as They Seem

Combustion Sources: From your stove to your cigarette, combustion sources spew pollutants like carbon monoxide and particulate matter into the air.
Household Products: Aerosol sprays (including beauty, hygiene and health products), air fresheners, chlorine bleach, detergents, dry cleaning chemicals, rug and upholstery cleaners, furniture and floor polish, and oven cleaners may emit harmful VOCs.
Pet Dander: If you have a furry pet, your Indoor Air Quality is also affected by pet dander – small particles of skin that animals with hair and fur shed from time to time.
Building Materials: Even the very materials your house is made of, pressed wood and asbestos, for instance, can slowly release pollutants.

Outdoor Pollutants: Unwelcome Guests

Airborne Invaders: External air-borne pollutants like particulate matter and gases like nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide, and volatile organic compounds can sneak indoors through open doors, windows, and ventilation systems.
Pollen and other biological pollutants: During certain times of the year, there is an increase in pollen in the outside air, which also makes its way into indoor spaces. These are suspended in the air, settling on furniture and inside HVAC systems. Bacteria, moulds, mildew, viruses and dust mites are present all year round.
Soil and Water: Groundwater and soil contamination aren’t just outdoor problems; they can invade your indoor space through your water supply system.
Human Factors: Even you could be a carrier, bringing pollutants inside on your clothes and shoes.

The Hidden Costs: IAQ’s Impact on Home and Health

Poor IAQ doesn’t just harm you; it can also sabotage the structural integrity of your home. Too much humidity fosters mould growth, while inefficient HVAC systems burdened by clogged filters can wear out prematurely.

Your furniture and books aren’t safe either. Poor indoor air quality can cause moisture damage, mould growth, fading, and discolouration. It can also attract pests that feed on wood, paper and glue. High humidity can lead to warping and cracking of furniture, while pollutants can stain and deteriorate materials. Upholstered furniture might also accumulate allergens and wear down due to dust and dirt.

Smart Tech for Smart Monitoring

In this digital age, technology has turned IAQ monitoring into a real-time activity. Portable devices equipped with sensors provide instant feedback on multiple variables. Some even sync with smartphone apps, giving you real-time control no matter where you are.

Legal and Policy Implications

As IAQ gains recognition, so do the legal frameworks surrounding it. Countries are establishing guidelines or even stringent standards, especially for public buildings and workplaces. Not keeping up can lead to financial and legal repercussions.

Building a Breathable Future

The architecture of tomorrow is being designed with IAQ in mind. Think low-VOC paints, natural fibre rugs, innovative oxidation methods and advanced, IoT-integrated ventilation systems. Using biophilic design principles, like incorporating natural elements into indoor spaces, can also enhance air circulation and reduce pollutants. Sustainable architecture isn’t just a trend; it’s becoming a necessity.

Community Matters: A Shared Responsibility

IAQ is not just a personal issue; it’s a societal one. Your neighbour’s poor IAQ could very well become your problem, particularly in densely populated areas. Community-wide solutions range from public awareness campaigns to outdated heating and cooking system upgrades. There is also a greater need to integrate IAQ education into school curricula and implement indoor air quality monitoring systems in public buildings and facilities to underscore the importance of maintaining clean air environments.

The Future is Clear: What’s Next for IAQ?

With IAQ technology evolving rapidly, the future holds promise for even smarter monitoring systems, further research into long-term health impacts, and innovative filtration technologies like nano-filters and bio-filters.

In closing

Understanding and monitoring IAQ is a matter of immediate and long-term health, impacting humans and the spaces they inhabit. Given the complex interplay of internal and external factors that affect IAQ, a multi-faceted approach to monitoring and improvement is crucial. As data shows, poor IAQ is a global health issue that requires concerted efforts for policy formulation and monitoring techniques.

What’s the Difference? Indoor Air Quality vs. Outdoor Air Quality

What is Air Quality?

Air quality refers to the composition and cleanliness of the air we breathe in our environment. Several air quality monitoring techniques are used to assess whether the air we breathe is safe and healthy. Understanding and maintaining good air quality is essential because it directly and profoundly affects our well-being, economic activities, and the planetary environment for the present and future generations.

When defining air quality, we distinguish between indoor and outdoor air quality. The distinction lies in their respective environments and sources of pollution, as well as the air quality monitoring techniques used in different contexts.

Outdoor air quality refers to the state of the atmosphere in open spaces, streets, and natural settings based on factors like vehicular emissions, industrial processes, natural events, and weather conditions. It receives significant attention due to its direct impact on public health and the environment.

On the other hand, indoor air quality pertains to the air within enclosed spaces, whose condition is determined by sources like cooking, heating, cleaning, and the presence of pollutants like dust mites, pet dander, and volatile organic compounds furnishings and materials. Indoor air quality is also affected by outdoor air entering indoor spaces, but indoor ventilation systems and lifestyle choices play a major role.


Good Air Quality VS Bad Air Quality:

Good air quality is when the atmosphere is clean, pure, and free from harmful pollutants. It means the air is fresh, with no unpleasant odours, haze, or obstructed visibility, allowing for comfortable, irritation-free breathing. Low levels of particulate matter (such as PM2.5 and PM10) characterise good air quality, and a bright blue sky often accompanies it.

In contrast, poor air quality is characterised by elevated levels of pollutants such as particulate matter (PM), ground-level ozone (O3), sulphur dioxide (SO2), carbon monoxide (CO) and nitrogen dioxide (NO2).

Why are Air Quality Monitoring Techniques so essential?

Health Concerns:

Monitoring air quality is primarily driven by a concern for human health. Poor air quality can severely affect human health, including respiratory conditions like allergies, asthma, bronchitis, cardiovascular diseases, liver problems and cognitive impairment. It can even cause lung cancer.

Environmental Impact: 

Air quality monitoring is also crucial for preserving the environment. Air pollution contributes to ecological problems, including acid rain and soil contamination, damages vegetation, and harms aquatic ecosystems. High levels of certain air pollutants, such as ground-level ozone, can harm forests and crops, affecting agricultural yields and forest health. Air pollution significantly contributes to climate change, as some pollutants, like methane and black carbon, are potent greenhouse gases. By tracking air quality, we can better understand and mitigate these environmental impacts and protect the planet for us and the future.

Compliance and Regulations: 

Governments and regulatory agencies use air quality monitoring data to enforce air quality standards to protect public health and the environment by limiting permissible levels of pollutants in the atmosphere. Monitoring ensures that industries, vehicles, and other emission sources adhere to these standards, facilitating compliance and allowing for corrective actions when necessary. It also provides the basis for air quality alerts and advisories, which inform the public about health risks during episodes of poor air quality.

Public Awareness and Education: 

Air quality monitoring fosters public awareness and education about the consequences of air pollution. Accessible data and real-time information empower individuals to make informed decisions about outdoor activities and travel routes, reducing their exposure to harmful pollutants. Additionally, educational campaigns and initiatives driven by air quality data promote environmentally responsible behaviour, such as reducing vehicle emissions and minimising pollutants in daily life.

A Look Back at the Evolution of Air Quality Monitoring Techniques:

Over the years, the tools and methods used to assess air quality have evolved significantly, enabling us to better understand and manage air pollution. Here’s a brief overview of the key milestones in the evolution of air quality monitoring techniques:

Early Observations and Perceptions (Pre-Industrial Era):
Before the Industrial Revolution, air quality monitoring techniques were primarily based on sensory perceptions. People relied on their senses to detect changes in air quality, like smoke, odours, and visible pollution from industrial processes.

The Birth of Chemical Analysis (Late 18th Century):
The late 18th century saw the emergence of chemical analysis as a method to study air quality. Scientists like Antoine Lavoisier began using chemical tests to identify and measure air components, including discovering oxygen and nitrogen.

Gravimetric Analysis (Early 20th Century):
In the early 20th century, gravimetric analysis became popular for quantifying airborne particulate matter. This technique involved collecting airborne particles on filters and weighing them to determine their concentration.

Development of Gas Analysers (Mid-20th Century):
Significant advancements were made in the mid-20th century with the development of gas analysers capable of measuring specific pollutants in the air. These analysers directly quantified sulphur dioxide, nitrogen dioxide, and carbon monoxide.

The Emergence of Air Quality Monitoring Networks (Late 20th Century):
In response to increasing concerns about global air quality, many countries established air quality monitoring networks during the late 20th century. These networks featured a distributed system of monitoring stations equipped with various instruments to track pollutant levels over time.

Real-Time Monitoring (Late 20th Century to Present):
The late 20th century and early 21st century saw real-time air quality monitoring systems implemented. These systems use advanced sensors and technology to provide continuous, up-to-the-minute data on air quality parameters. This real-time information is crucial for issuing air quality alerts and informing the public about health risks.

In Closing:

In recent years, remote sensing and satellite technology have played a larger role in air quality monitoring. Satellites equipped with sensors can provide a bird’s-eye view of outdoor air quality on a regional or global scale. Citizen science initiatives and the proliferation of mobile apps have also democratised air quality monitoring techniques.

Users of IAQ tech can now contribute to data collection efforts using Indoor Air Quality monitors, which will enhance our understanding of localised air quality and potential sources of pollution.

Where Do They Come From? The Origins Of Common Indoor Air Pollutants


The air we inhale is teeming with particles and compounds that profoundly impact our health and well-being. By using appropriate air quality monitoring techniques, we learn about these pollutants and their origins to create a cleaner, safer environment for ourselves and future generations.

This comprehensive guide delves into three of the most common pollutants – Particulate Matter, Volatile Organic Compounds, Carbon Dioxide, and its deadly counterpart, Carbon Monoxide. We’ll also explore the origins of pollutants like radon and ozone and biological agents like mould and mildew.

What is Particulate Matter?

Particulate Matter (PM) refers to microscopic particles or droplets in the air. They differ in size, composition, and origin. PM is categorised by size, with the two main classifications being PM2.5 and PM10.

PM2.5 refers to fine particles 2.5 micrometres or smaller in diameter. They originate from combustion processes like fossil-fuel burning in vehicles and power plants, industrial emissions, natural sources like wildfires, dust storms, and volcanic eruptions, and chemical reactions in the atmosphere (such as the conversion of sulphur dioxide into sulphate particles).

PM2.5 can invade the respiratory system and even enter the bloodstream, causing severe cardiovascular effects, lung cancer, and premature death, especially in areas with high fine particle pollution.

PM10, which includes particles with a diameter of 10 micrometres or smaller, originates from natural sources like dust storms and volcanic eruptions, human activities such as construction and industrial processes, and combustion of fossil fuels and biomass in vehicles and power plants.

Particulate matter of all kinds contributes to environmental issues, including reduced visibility (haze), damage to ecosystems, and the formation of acid rain. It can also transport harmful chemicals, heavy metals, and organic compounds, making it a complex and significant component of air pollution.

What Are Volatile Organic Compounds?

Volatile Organic Compounds (VOCs) are a heterogeneous group of organic chemicals that can quickly evaporate into the air at room temperature. They have high vapour pressure, so they can readily transition from a liquid or solid state into a gas or vapour. VOCs are standard indoor and outdoor air pollution components and can originate from natural and human-made sources.

Here are some common VOCs and their sources:

  • Benzene: Found in gasoline, vehicle emissions, and tobacco smoke.
  • Formaldehyde: Emitted from building materials, adhesives, and combustion processes.
  • Toluene: Present in paints, solvents, and gasoline.
  • Xylene: Used in paint thinners, sealants, and some printing processes.
  • Ethylbenzene: Found in vehicle exhaust and some industrial processes.
  • Methylene Chloride: Used in paint strippers and aerosol spray propellants.

Long-term exposure to certain VOCs is associated with an increased risk of cancer, neurological issues and liver and kidney problems.

What is Carbon Dioxide (CO2)?

Carbon Dioxide, or CO2, is a colourless, odourless gas composed of one carbon atom (C) and two oxygen atoms (O). It is a naturally occurring component of Earth’s atmosphere, making up a small fraction of our air. Essential for life on Earth because it is involved in photosynthesis, CO2 helps build the foundation of the planet’s food chain.

CO2 enters our atmosphere through natural processes (volcanic eruptions, respiration, and decay) and human activities (burning fossil fuels, deforestation, and industrial processes). Incomplete combustion processes in gas stoves, water heaters, and furnaces can also generate CO2 indoors.

CO2 is crucial  to keeping our planet habitable, but it also has more than its fair share of drawbacks. Being a greenhouse gas, it traps heat in the Earth’s atmosphere. Excessive CO2 emissions from human activities are the primary catalyst of global warming and the climate crisis.

In average atmospheric concentrations, CO2 is not harmful to human health. However, in confined, under-ventilated spaces, elevated CO2 levels can lead to dizziness, shortness of breath, and impaired cognitive function.

What is Carbon Monoxide (CO)?

Carbon Monoxide (CO) is a colourless, odourless, and tasteless gas consisting of one carbon atom (C) and one oxygen atom (O). It is formed primarily through incomplete combustion processes, where carbon-containing fuels like wood, gasoline, natural gas, and coal do not burn completely, producing CO instead of carbon dioxide (CO2). Familiar sources of CO include vehicle exhaust, gas stoves, furnaces, fireplaces, and faulty or poorly maintained combustion appliances.

Carbon monoxide is very toxic for humans and animals. When inhaled, it binds to haemoglobin in red blood cells, reducing the blood’s ability to carry oxygen. Symptoms of CO poisoning include headache, nausea, dizziness, confusion, and, in severe cases, unconsciousness and death.

Proper ventilation, routinely maintaining fuel-burning appliances, using CO detectors in homes, and not idling vehicles in enclosed spaces can prevent CO poisoning.

What is Radon?

Colourless, odourless, and tasteless, radon is a radioactive gas. The degeneration of uranium and thorium in the Earth’s crust produces radon. It can enter houses and buildings through cracks in the base, gaps around pipelines, and other entry points. In poorly ventilated indoor spaces, radon can accumulate to dangerous levels. Proper ventilation and radon testing are essential to reduce exposure to this dangerous pollutant, one of the key factors behind lung cancer.

What Is Ozone?

Ozone, or O3, is a molecule made of three oxygen atoms. The ozone in the Earth’s stratosphere protects us from the sun’s ultraviolet radiation, but ground-level ozone is a component of air pollution. Ground-level ozone is not emitted directly but develops in the atmosphere through chemical reactions involving precursor pollutants like nitrogen oxides (NOx) and volatile organic compounds (VOCs).

It can exacerbate asthma and other respiratory conditions and is regarded as a key concern in areas with high levels of air pollution.

What are Biological Pollutants (Mould and Mildew)?

Mould and mildew are categories of fungi that can grow indoors when there is excess moisture. They often appear as patches of discolouration or as a fuzzy, thread-like growth on various surfaces, such as walls, ceilings, and damp areas. 

Humans and animals unknowingly inhale pores released by mould and mildew, which lead to nasal congestion, coughing, sneezing, skin rashes, and eye irritation. In more severe cases, mould exposure can cause fungal infections in those who are immunocompromised.

In Closing

This rich tapestry of pollutants that affect the quality of our air can be measured and managed with a number of practical solutions, both at a macro and micro level. New tools and strategies are constantly emerging to help tackle the harm caused by these pollutants and create a cleaner environment for all of us.

In the next part of this blog post, we’ll explore modern technologies and scientifically proven air quality monitoring techniques to combat the effects of these pollutants on our indoor air quality.

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