How everyday activities impact indoor air quality in homes: insights from the K-HEALTHinAIR project

Introduction

What is the K-HEALTHinAIR project?

The K-HEALTHinAIR project is a European research initiative aimed at improving indoor air quality (IAQ) and, in turn, people’s health. Through real-time monitoring and data analysis, the project seeks to identify the factors that affect air quality in different environments, proposing innovative solutions that can be implemented both at individual and institutional levels. Homes are one of the key areas of study since we spend a significant portion of our time indoors, and indoor air quality can directly influence our health and well-being.

Why indoor air quality matters

The quality of the air we breathe inside our homes has a significant impact on our health and well-being. As we spend most of our time in enclosed spaces, ensuring that the air is clean and free of harmful pollutants is essential. Parameters like particulate matter (PM_2.5), volatile organic compounds (VOCs), and, in some way, carbon dioxide (CO₂) can negatively affect respiratory health, increasing the risk of issues such as allergies, asthma, and, in severe cases, chronic respiratory diseases. Maintaining clean indoor air is vital for long-term health, and the K-HEALTHinAIR project aims to shed light on how our daily activities influence air quality inside our homes.

What we aimed to discover

Study goals

The primary goal of this study was to understand what factors affect indoor air quality in homes. Specifically, we focused on kitchens, as they are spaces where indoor air quality can change rapidly due to various daily activities like cooking, cleaning, and eating. By monitoring these activities and their impact on air quality, we aimed to identify the main sources of pollution inside homes and how they vary depending on lifestyle and habits.

How we conducted the study

Setting up sensors

To monitor IAQ, we placed air quality sensors in the kitchens and living rooms of seven homes for a period of two weeks. While both areas were monitored, kitchens proved to be more interesting for this study, as they are typically where activities that significantly affect air quality, such as cooking or cleaning, occur most frequently. The sensors continuously monitored multiple parameters like temperature, humidity, CO₂, Total VOC, formaldehyde, and PM_2.5.

Daily activity logs

In addition to the sensors, the homeowners were asked to keep a detailed log of their daily activities. This included noting down when they were cooking, cleaning, smoking, or any other relevant activities that might affect the air quality. This data helped us link specific activities to changes in air quality levels, providing deeper insights into the relationship between what we do indoors and the air we breathe.

Analysing the data

Once the data was collected, we began by looking at basic trends to understand the overall patterns in air quality. From there, we used advanced computer techniques, such as machine learning, to find hidden patterns in the data that might not be obvious at first glance. These techniques allowed us to create easy-to-read visuals showing how everyday activities impact indoor air quality in a clear and accessible way.

Key discoveries

Different lifestyles, different air quality

One of the main findings of the study was the significant variation in air quality between different homes. Each household had its own unique set of habits and daily activities, which influenced the levels of indoor pollutants. For example, homes with frequent cooking or smoking showed higher levels of pollutants, while other homes with more regular ventilation practices maintained better air quality. This variability highlights the importance of understanding how lifestyle choices directly affect the air we breathe indoors.

Top air pollutants identified

The data collected from the sensors revealed that PM_2.5 and total VOCs were the most common pollutants in the kitchens of the homes we studied. These pollutants are especially concerning because they can have negative effects on respiratory health, particularly in children, the elderly, and those with pre-existing conditions.

Impact of daily activities

Our analysis showed that most daily activities had a negative impact on indoor air quality, with smoking and cooking standing out as the activities with the largest negative effects. Smoking, in particular, caused a sharp rise in pollutant levels, while cooking also contributed to increased levels of the pollutants. On the other hand, opening windows or using proper ventilation was found to be the most effective way to mitigate these effects.

The use of kitchen extractor hoods during cooking also helped reduce the concentration of pollutants, though their effectiveness depended on proper usage. Activating the hood at the start of cooking and keeping it running for a sufficient time afterward, especially when combined with opening windows, significantly improved air quality.

Visualising the results

Using colour annotations

To make the results of our study more understandable, we used colours to visually represent the impact of different activities on indoor air quality. Each activity, such as cooking, cleaning, or smoking, was assigned a distinct colour on the corresponding data plots. Specific colour-schemes were also applied to the time of activities and IAQ parameters PM_2.5, CO₂, and total VOCs. A combined analysis of activity type, activity time, and IAQ parameter plots allowed us to track how air quality changed throughout the day. This visual approach made it easy to see when air quality worsened and which activities were responsible.

One of the key metrics we used in this study was the IAQ Indicator. This indicator is a composite measure calculated from levels of PM_2.5, total VOCs, and CO₂. It provides a simple way to assess overall air quality, with higher values indicating better air quality and lower values indicating poorer air quality.

Figure 1. Distribution of the IAQ Indicator for various activities across all homes. The figure highlights how smoking and eating lead to a sharp decrease in air quality, while ventilation improves it.

For example, Figure 1 illustrates how the IAQ Indicator varied depending on the activity taking place in the kitchen. Each box represents a different activity or a combination of activities, and shows the distribution of the IAQ Indicator values. The figure clearly demonstrates how certain activities, such as smoking and cooking, led to more frequent poor air quality (lower IAQ Indicator values), while others like ventilation helped improve it.

Identifying specific times and actions

By looking at visual representations of the IAQ Indicator distribution and activity times, we were able to pinpoint specific times of day and actions that led to poor air quality. The colour-coding made it easy to identify how activities like cooking without using proper ventilation or smoking indoors caused sharp decreases in IAQ Indicator. Figure 1 also highlights the importance of ventilation, as activities that included proper ventilation resulted in a significantly smaller negative impact on air quality. This shows that maintaining good airflow in the home is crucial for minimizing indoor air pollution.

What this means for our health and future research

Health implications

Long-term exposure to these pollutants can lead to aggravated respiratory conditions such as asthma and allergies, and in more severe cases, it can contribute to the development of chronic respiratory diseases[1]^,[2]. This is especially relevant for vulnerable groups such as children, seniors, and those with pre-existing health conditions.

While activities like cooking and cleaning are essential parts of daily life, it’s crucial to adopt practices that minimise their impact on IAQ. Proper ventilation and the use of extractor hoods during cooking can significantly reduce the concentration of harmful pollutants and improve the air we breathe.

One of the most preventable contributors to poor indoor air quality is smoking. Smoking indoors releases large amounts of harmful particles and chemicals that significantly degrade air quality and pose serious health risks.

Next steps

Our next steps in the K-HEALTHinAIR project involve integrating health data into future studies to better understand the direct link between indoor air quality and health outcomes. By combining sensor data with information on residents' health, we aim to identify specific thresholds for air pollutants that may pose risks to health and develop more targeted recommendations for improving indoor air quality. Additionally, expanding the study to include a wider range of indoor environments, such as schools and offices, will provide a broader understanding of how indoor air quality affects different populations.

Conclusion

Summary of findings

This study highlights how everyday activities inside the home significantly impact IAQ. Activities such as cooking, smoking, and cleaning were shown to have the most detrimental effects, increasing levels of particulate matter and volatile organic compounds which are known to have serious health implications. On the other hand, proper ventilation, including the use of extractor hoods and opening windows, proved to be an effective method for reducing the build-up of indoor pollutants. The results emphasize the need for improved awareness and adoption of better ventilation practices during daily routines to mitigate the risks of poor air quality.

Looking ahead

Maintaining clean indoor air is vital for long-term health, particularly for vulnerable groups such as children, seniors, and individuals with respiratory conditions.

To better understand these impacts, the K-HEALTHinAIR project will expand its research to include health data, establishing clearer connections between indoor air quality and health outcomes. Additionally, the project will study various indoor environments, like schools and offices, to gain a broader understanding of how air quality affects different populations, ultimately aiming to develop targeted interventions to protect public health.

References

[1] According to the WHO Global Air Quality Guidelines, long-term exposure to PM2.5 is strongly associated with cardiovascular diseases, stroke, and respiratory illnesses like asthma and chronic obstructive pulmonary disease (COPD). PM2.5 particles can penetrate deeply into the lungs and enter the bloodstream, affecting not only the lungs but also the heart and other organs. Long-term exposure has also been linked to lung cancer development.

[2] Volatile Organic Compounds (VOCs), while less studied than particulate matter, are also a significant concern. Some VOCs, such as benzene, are known carcinogens, and chronic exposure to high levels of VOCs can lead to respiratory issues, damage to the nervous system, and other long-term health effects. These compounds originate from everyday activities like cooking, smoking, and using household products.