ResearchIndoor air quality study: Cooking can cause pollution three times worse than London roads

Air quality study by Zehnder UK shows the staggering pollution levels caused by indoor activities.
Content Team5 years ago9 min

Indoor Air Quality (IAQ) is dangerously compromised by seemingly mundane everyday tasks such as cleaning, cooking and spraying aerosols, a study by heating and ventilation specialists Zehnder UK shows.

Alongside more obvious causes of poor IAQ such as smoking and vaping indoors, these factors all have a significant impact on the levels of pollutants we breathe inside our homes.

Levels of PM2.5 particles (air pollution) recorded in different environments. Source: Zehnder UK using Awair monitor
Levels of PM2.5 particles (air pollution) recorded in different environments. Source: Zehnder UK using Awair monitor

Volunteers with different home environments and lifestyle habits were chosen as in-depth subjects for the study. An indoor air quality monitor₁ was placed in each subject’s house for a total of five days, recording dust particles, chemicals and humidity.

The data was collected from a number of areas in each property including the kitchen, bedroom and living room. The data highlighted significant spikes in levels of PM2.5 particles, fine dust molecules that can lead to serious health conditions such as respiratory diseases including asthma, allergies, dementia, mental health issues and insomnia. The air quality monitor used categorises PM2.5 levels, which is measured in micrograms per cubic metre (µg/m³) as follows:

Cooking meals such as omelettes, stir-fries and grilled foods raised pollution levels in the kitchen to over three times that of a typical London road


  • 0-15 = good (safe)
  • 16-35 = fairly good
  • 36-55 = fair
  • 56-75 = fairly poor
  • 76+ = poor (harmful)

The study showed that cooking meals such as omelettes, stir-fries and grilled foods raised pollution levels in the kitchen to over three times that of a typical London road. Using hairspray when getting ready in the morning for example also caused a huge spike in harmful dust particles.

It is to be expected that smoking inside would cause an increase in pollutants, but the study showed just how dramatic that increase is, with both cigarette and vape smoke taking levels to over 65,000 times higher than is considered normal, even with an extractor fan in the same room.

Rupert Kazlauciunas, technical product manager at Zehnder UK, comments on the findings:

“We are constantly made aware of the dangers of outdoor pollution, but IAQ is dangerously overlooked. We spend as much as 90% of our time indoors – yet mention air quality and our thoughts immediately turn to large lorries pumping fumes, cars clogging our roads or factories belching out smoke.

“The chemicals and particles we breathe in our homes and workplaces actually pose a far more dangerous threat to our health than most people realise. Smoking, perhaps, is not a huge surprise, but cooking, using cosmetics and even just having pets or vacuuming our carpets can raise dust particles to harmful levels. The more we can do to tackle indoor pollution, through educating people and the use of innovative ventilation products, the better position we put ourselves in to protect future generations.”

Case studies

Smoking inside 

One of the study’s subjects, a smoker, was joined one day by friends, also smokers, who all smoked inside his home throughout the evening. Over a period of two hours, the PM2.5 level jumped from a safe level of 1.3µg/m³ to a staggering 839µg/m³ (almost 65,000% increase).A dangerous level of PM2.5 is considered to be anything over 76µg/m³ and the average level recorded in London by the roadside is 23µg/m³, according to government data.

Frying and grilling food

Another participant recorded consistently low levels of PM2.5 throughout the study but experienced a peak of 68µg/m³ when cooking an omelette and using the grill on one occasion. Again, compared to outdoor pollution levels, this figure is over three times higher than those recorded by a London roadside.

Using hairspray and vaping 

Another participant had the monitor in his bedroom on one day of the study, which recorded a large spike in both chemical and PM2.5 levels at around 7am, when his wife was using hairspray as she got ready for the day. The level recorded was 85 µg/m³, over 5 times the safe limit of 15 µg/m³. This level was also recorded later in the day, coinciding with the participant vaping in the same room.


Zehnder’s study was conducted across five different homes, each with a different set of variables (pets, no pets, windows open, windows closed, ventilation fans and units on and off etc). Each subject had the device for 5 days and took a diary during that time, detailing activities and variables.

To find more indoor air quality content, click here

Zehnder Group UK designs and manufactures a full range of indoor climate solutions for residential, commercial and industrial properties, designed to provide comfort, energy efficiency and wellbeing.

Content Team

Work in Mind is a content platform designed to give a voice to thinkers, businesses, journalists and regulatory bodies in the field of healthy buildings.

Subscribe to our newsletter