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Gas cooking impact on indoor air quality: Cairsens® micro-sensors used for largest-ever study conducted in Europe
Indoor air quality | Cairsens® micro-sensors
CLASP is an international non-profit organization, focused on improving the energy and environmental performance of household appliances, to ensure they are planet-neutral and people-positive.
CLASP is data driven, providing technical analysis and evidence to advise governments around the world on setting ambitious appliance efficiency policy.

Following recent studies made in the United States on health and environmental impact of gas cooking on indoor air quality, CLASP was funded by the European Climate Foundation to determine how gas cooking impacts European households, gathering evidence to raise awareness of air quality risks and to inform policy change in Europe. They partnered with the Netherlands Organisation for Applied Scientific Research (TNO) on this project.

In the first phase of the study (Mid-may/dec 2022), TNO conducted a literature review on the health harms of gas cooking; a computer simulation to compare indoor air pollution in gas and electric cooking homes; and carried out lab tests on gas hobs to determine pollution levels emitted by the product. The findings were used to draw up the specifications for the second phase (field testing), that is defining what pollutants needed to be measured, settling on NO2, CO, and PM2.5, with what type of sensors, in how many households, etc.
The benchmark of sensors found on the market featured the review of Airlab challenge (Airparif) and AQMD (state of California). These showed ENVEA Cairsens micro-sensors had a very good grading (based on measurement quality, metrology, ease of use, etc.) for NO2 and CO.
In the end, TNO research led the project’s panel of experts to select several sensors – including ENVEA Cairsens for NO2 and CO – that could fit the field test requirements. First contact was then made with ENVEA to confirm the technical specs and delivery capabilities.

Field Text Phase

CLASP received funding in November 2022 to conduct the field testing study, the second phase of their project. The objective was to measure emissions from residential cooking appliances in the kitchen, and to assess gas vs electric cooking impacts on indoor air quality, specifically compared to the WHO Air Quality Guidelines and EU/UK Air Quality Standards. In order to do this, CLASP and its partners conducted in-home testing in 247 households across 7 countries (IT, ES, FR, NL, UK, SK and RO). The objective was to capture 32 gas-cooking and 8 electric-cooking households in each country. Tests took place from end of January until end of May 2023
Households were selected by Opinium Research and provided with a portable test kit featuring the sensors (see video below), a tutorial video explaining how to set up (and then remove) the sensors, as well as detailed questionnaires to capture their home specificities, daily cooking habits, etc. They were asked to provide pictures of the sensor set up, their cooking throughout the day, and what type of ventilation they were using, if any.
Sensors in a kitchen during the field tests (Copyright TNO)

Key findings of the Field Study

  • Extrapolating to a year, 25% of the households cooking on gas exceeded the WHO 1-h guideline value for NO2. While none of the households cooking on electrical hobs did
  • Over 57% of gas cooking households exceeded the WHO daily limit for NO2. Added together, the WHO daily limit was breached for 3.25 days over the 13-day testing period, on average. Nearly 16% of electric-cooking homes exceeded the WHO’s daily limits, but these homes were often in areas with higher outdoor air pollution.
For the full details on the findings, read CLASP press release.

Download TNO report on the field study.

Interview with Piet Jacobs, senior researcher at TNO.

Why were ENVEA CO & NO2 micro-sensors chosen?

“The field tests were meant to help us answer a few questions. Indeed, we wanted to check if there were significant differences in NO2, CO and PM2.5 concentrations between household cooking on gas or electric. And check the potential exceedance of World Health Organization (WHO)/EU guidelines and limit values for NO2, CO and PM2.5.
In order to answer the former question, we decided to use passive gas tubes placed in several locations (in the kitchen, living-room, bedroom and outside). However, since these can only provide a 2-week average gas concentration, they would not help us answer the latter question and gather data to compare with daily and hourly standard values set by WHO. That’s why the ENVEA Cairsens micro-sensors were a good fit for us to use since they provide a high time resolution (1 minute). Their compact design was also a positive factor so the households could use them easily in their daily kitchen routine.”

Can you give us a quick feedback on the tests?

After each round of measurement we calibrated the sensors in our lab using real-condition gas hob and we noted the CO measurements showed some discrepancies with the CO calibration slope. Turns out, we tested alcohol-based products such as cleaning tissues, cleaning gel, red wine etc. and saw clear peaks at the times these were used when measuring CO emitted by the gas hob. Everyone was surprised by the amount of alcohol involved in the cooking process leading to disruptions in the CO measurement. The cross sensitivity of the sensors to alcohol or Volatile Organic Compounds (VOC) emitted in a kitchen while cooking appears to be pretty high, therefore making the CO measurement not quite adapted for this kind of study.”

To your knowledge, will there be any further studies on the topic?

“The interest on gas cooking emissions is a topic that is growing in many countries. In any case, following up the survey, I was contacted by researchers from 2 universities in Spain (Castellón de la Plana de la Plana) and USA (Berkley) to use the Cairsens micro-sensors for their projects.”

According to a separate consumer survey conducted by CLASP and Opinium Research in Romania, France, Spain and the UK, if made aware of the health risks of pollution from gas cooking, up to three quarters of respondents (74%) say they would consider getting rid of their gas appliances. Having access to indoor air quality data is therefore not only important to inform policy, but also to inform people’s cooking appliance decisions.

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