Measuring Outdoor Air Quality

Measuring Outdoor Air Quality

With warm weather approaching in many parts of the world, people will be looking to spend more time outside. Research has shown that being outdoors in nature can reduce stress levels, cortisol levels, muscle tension and heart rate, helping to reduce cardiovascular disease risk.1 Yet, despite the benefits to our physical and mental health, many people spend as little as 4-7 minutes outside each day.2

Air pollution may be one factor keeping some people from spending more time outside, depending on where you live. By some estimates, as many as 7.8% of deaths across the globe can be attributed to outdoor air pollution, representing more than 4.5 million people.3 Older people are typically the most susceptible group to the effects of air pollution.

Long-term exposure to air pollution can impact cognitive function and has been linked to stroke, heart disease, lung cancer and respiratory diseases like asthma and COPD.4,5 Due to industrialization, middle-income countries tend to have the highest death rate from outdoor air pollution and the greatest exposure to particulate matter, tiny liquid droplets or solid particles in the air like smoke, dust and soot that can be inhaled.6

Ambient air quality and sources of outdoor air pollution

Measuring outdoor air quality around the world is critical to arm people, companies and governments with the knowledge they need to understand how safe the air is and what actions need to be taken to improve air quality. According to the U.S. Environmental Protection Agency (EPA), ambient air quality monitoring is the systematic, long-term assessment of pollutant levels.7 The goal is to measure the amount and type of pollutants in outdoor air, such as particulate matter, carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and volatile organic compounds (VOCs).8

Data has shown that individuals’ behaviors and the actions of key industries directly impact outdoor air quality. For instance, during COVID-related lockdowns in April 2020, the European Union saw NO2 concentrations at traffic stations fall by up to 70% because fewer vehicles were on the road.9

It is estimated that around 60% of Europe’s Sulphur oxide emissions, including SO2, come from energy production and distribution (i.e., power plants burning fossil fuels).10 Ground-level O3 pollution can come from a number of sources, including vehicles, power plants, industrial boilers, refineries, chemical plants, lawn equipment and even household paints and cleaners.11

How widespread is ambient air quality monitoring?

Better understanding our air quality, and improving it for future generations, is a growing need in today’s environment. Available data from the European Environment Agency (EEA) shows that there are at least 5,000 urban air monitoring sites and 800+ regional air monitoring sites across the EU.12 In the U.S., approximately 1,000 out of 3,000+ counties have air quality monitoring data.13

This data can come from fixed systems at weather stations, public buildings or traffic lights; there are also a growing number of portable air quality measurement systems that can be transported from place to place depending on the need.

Sensors vital to accurately monitoring outdoor air quality

Among the different technologies needed to create an ambient air quality monitoring system, its sensors are some of the most critical. Ambient air quality (AAQ) sensors should be able to detect low concentrations of a pollutant and see tiny changes in gas concentration, allowing them to convey highly accurate information to end-users. They should also maintain their accuracy wherever they are installed, whether in a forest or a dense urban setting. In addition, these sensors should:

·         Be durable enough to withstand the weather: Because systems are installed outdoors, they will see fluctuations in temperature and humidity and conditions like rain, snow, wind and sleet. The sensor should be engineered to reliably withstand these rugged conditions.

·         Be able to integrate in multiple applications. AAQ sensors could be in a mini fixed system, a mobile monitoring system or even in an unmanned aerial vehicle. The sensors should therefore be as compact in size and lightweight as possible to accommodate these different needs, as well as mechanically robust so they can be designed into various types of systems.

·         Have minimal false alarms. It is important for sensors to have minimal cross-sensitivity with other gases, meaning they detect the gas they are meant to detect and do not provide wrong information or false alarms to end-users.

·         Have reduced baseline drift. There is cost, time and effort involved in frequently recalibrating a sensor due to environmental impacts. Selecting a durable sensor with low drift means there is less time and money spent on calibration.   

To learn more about Honeywell’s AAQ sensors and how we are a pivotal part of ambient air quality monitoring efforts around the world, visit our website or contact us today.



1 – www.fs.usda.gov/features/wellness-benefits-great-outdoors#:~:text=Studies%20also%20show%20that%20being,risk%20factors%20for%20cardiovascular%20disease

2 - https://earthlab.uw.edu/2019/06/spend-time-outdoors-this-summer-to-reap-health-benefits  

3 - www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30752-2/fulltext

4 -  www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30752-2/fulltext

5 - www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health

6 - www.cdc.gov/air/particulate_matter.html

7 - www.epa.gov/air-quality-management-process/managing-air-quality-ambient-air-monitoring

8 - www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health

9 - www.eea.europa.eu/publications/status-of-air-quality-in-Europe-2022/europes-air-quality-status-2022

10 - www.eea.europa.eu/themes/air/air-pollution-sources-1

11 - www.azdeq.gov/ground-level-ozone-o3-pollution#:~:text=Ground%2Dlevel%20ozone%20(O%203,solvents%2C%20and%20motorized%20lawn%20equipment.

12 - www.eea.europa.eu/publications/92-9167-058-8/page010.html#:~:text=Totally%2C%20the%20number%20of%20air,more%20than%20800%20regional%20sites

13 - https://www.epa.gov/outdoor-air-quality-data/frequent-questions-about-airdata