Does your kitchen smell? How and why you should get rid of the smells ?

The kitchen is a place we use numerous time a day, paying relatively little attention to the potentially harmful effects of the smells that are present. More or less pleasant, more or less persistent, these odours are generally perceived as a harmless consequence of cooking and handling ingredients and other products. These odours stem from volatile compounds found in certain substances, which diffuse into the air. Can these molecules be harmful? How can we protect ourselves?

While it is well-known that certain fuels, like charcoal or wood, release toxic substances¹, the health impacts of preparing a simple meal, even using conventional combustion methods, remain largely unknown to many. A number of scientific studies have addressed the issue of indoor air pollution in the kitchen, and in this article we propose a few lessons and the best practices to protect your health and that of your loved ones, and limit odour-related discomfort.

I – Kitchen smells: a simple olfactory annoyance or a health risk?

An unpleasant smell, coming from road traffic or an industrial site, is often a source of concern. Conversely, the kitchen, with its pleasant smells, is rarely identified as a place where the air is saturated with toxic particles. Yet there is no systematic link between olfactory discomfort and health risk:

• In some cases, an unpleasant odour is harmless: for example, the smell of rotten eggs is identified by our sense of smell at concentrations 500 to 1000 times lower than the threshold level of the hydrogen sulfide from which it comes;
• By contrast, some toxic molecules are completely odourless, such as carbon monoxide, a byproduct of incomplete combustion that can be lethal.

Moreover, prolonged or repeated exposure to unpleasant smells can also affect health by causing stress and reducing well-being.

In 2018, researchers at the University of Colorado launched a study to assess the impact of daily activities on indoor air quality². Among the cases analysed, they tested the pollution emitted by cooking a full Thanksgiving dinner, where vegetables and meats are usually grilled or roasted. First surprise: pollutant concentrations were so high that they had to adjust the settings of their measuring devices!

During the hour following the preparation of the dinner, the level of fine particles, PM2.5, likely to penetrate the respiratory tract, was 200 micrograms/m³, i.e. 5 times higher than that of the city of Paris , and almost identical to that of Calcutta, the 2nd most polluted city in the world! Exposure continues during the post-cooking degradation phase, and may even exceed that of the cooking period itself. Particle levels decrease progressively and, in the study cited, the WHO-recommended threshold of 10 micrograms/m³ was reached after more than 8 hours.

The researchers also modeled the respiratory deposition of particulate matter for an adult staying 12 hours in the kitchen of the test house: it would measure 7 micrograms with no other indoor activity, but could rise to 68 micrograms during a 'typical' day accounting for three meals and the associated clean-up times, to reach 149 micrograms for a simulated Thanksgiving meal².

Another study³ measured the emissions of fine and ultrafine particles from 33 cooking sessions in Hong Kong homes, using traditional Chinese ingredients and recipes, spread across 12 naturally ventilated ovens. After cooking, the concentration of fine and ultrafine particles was 10 to 40 times higher than it was before, reaching a maximum average of around 160 micrograms/m³ in the kitchen. This pollution peak lasted about an hour and a half. The particles emitted by cooking spread to other rooms in the house, impacting the health of all residents, including children and people with respiratory problems, who might think they are protected from this pollution by staying away from the kitchen when it is in use. Particle levels in the living room reached around 60 micrograms/m³ for an hour. In Hong Kong, it is estimated that the kitchen is responsible for 62% of PM2.5 fine particle pollution within homes.

II - What factors contribute to kitchen smells and air pollution in the kitchen?

Fumes from gases, oils, charred ingredients and residue on cooking utensils, as well as particles released during the combustion process, form a mixture that generates kitchen smells and can be toxic. Several factors have an impact on the effects of cooking on health:

• Ingredients

Foods with a higher fat content release more pollutants⁴, with distinctions to be made within these ingredients: not all oils affect indoor air quality in the same way. Despite its pleasant taste and aroma, olive oil releases a significant number of fine particles when heated⁵.

• Cooking

The cooking method, along with the duration and temperature, can affect air quality; roasting, grilling, or frying tend to release more fine particles, while steaming or boiling is gentler on our lungs and creates fewer kitchen smells.

• The fuel used

According to several studies, cooking with gas has a greater impact on indoor air quality than cooking with an electric cooker, even though fine particles are released by both types of appliance. Some American⁶ and European⁷ studies even accuse gas cooking of being responsible for over 12% of cases of childhood asthma. In France for example, with approximately one-third of homes using gas stoves, the TNO report⁷ estimates that 140,000 cases of childhood asthma may be attributable to this cooking method.

Families using gas for cooking exceed the WHO's recommended daily exposure limit for nitrogen dioxide (NO₂) on average five days a week. Gas hobs also emit pollutants that are known to cause health effects, such as carbon monoxide and ultrafine particles. Another study⁸ showed that PM2.5 concentrations in the kitchen exceeded 1000 micrograms/m³ when several gas appliances were used: frying on the stove, sautéing in oil on a burner, or baking lasagna in the oven, with CO concentrations during cooking periods exceeding 9 parts per billion (ppb). NO₂ levels exceeded 50 ppb in some tests, and were as high as 400 ppb in an oven cleaning test, exceeding the Air Resources Board's recommendations for indoor air quality standards. Formaldehyde levels were also higher than these recommendations during certain actions such as grilling fish or cleaning the oven.

• Maintenance of kitchen appliances

Indoor air pollution in the kitchen will be greater if ovens, cookers and other appliances are poorly maintained or poorly ventilated. The convenience of self-cleaning kitchen appliances is appealing, but beware of their impact on health! Burning waste produces numerous fine particles, such as NO₂, carbon monoxide, and other pollutants, in potentially harmful concentrations.

III – How can you preserve indoor air quality in your kitchen while keeping kitchen smells at bay?

Of course, natural ventilation and fresh air are essential for limiting indoor pollution, whether in the kitchen or in other areas of your home. But the weather doesn't always lend itself to cooking with the window open! Some helpful practices can improve the air quality in your kitchen and eliminate smells:

• When designing a new kitchen, make sure that the ventilation systems provided are effective.
• When replacing your kitchen appliances, opt for appliances that use cleaner fuels
• In your cooking practices, use the healthiest cooking methods, particularly those using water (steaming, boiling, etc.) and avoid grilling or deep-frying
• Limit cooking time to just what is necessary
• Use an extractor hood
• Reduce other pollutants, especially from cleaning products, by selecting the least harmful options available
• Ensure that your kitchen appliances are properly maintained and ventilated, without resorting to self-cleaning versions
• Keep children and people with sensitive respiratory systems out of the kitchen while it is being used and cleaned
• To guide your improvements, you can also monitor the air quality in your kitchen by installing measuring devices.

These good practices are the essential basis for good air quality and the reduction of kitchen smells, but they are not always enough to deal with the pollution peaks generated by cooking and cleaning. So should you stop cooking? Of course not! But you do need to equip yourself accordingly. To reconcile the pleasure of cooking with the health and olfactory comfort of residents, we recommend installing an air purifier. It will provide the following benefits:

• Eliminating the main pollutants: fine particles, gases, dust, etc.
• Reducing kitchen smell
• Limiting the spread of these pollutants and kitchen smell to other rooms in the house.

Several air purifier technologies exist. Not all of them work on the same types of pollutants, and you need to take the characteristics of each one into account to make the right choice for your needs. You can read our complete guide to choosing the right air purifier.

IV - The benefits of TEQOYA air purifiers for your kitchen

Our air purifiers work by generating negative ions, which naturally occur in the environment, to charge and remove pollutants from the air. This perfectly silent technology is effective on 99.9% of polluting particles: urban pollution, viruses, bacteria, allergens, mould, ultrafine particles, dust, smoke, pollen, odours, VOCs, and more. To combat the high levels of pollutants typically found in kitchens, we've developed the TEQOYA E500. This supplements particle ionisation with an electrofiltration system: once charged and weighed down by negative ions, the pollutants are pressed against the electrofilters and captured. There are several levels of adjustment, so the air purifier can be adapted to varying conditions throughout the day:

• At the lowest level, it will be silent and purify the air in the room.
• When cooking or cleaning, the highest level will capture pollutants and odours, protecting your lungs and your comfort throughout the house. This setting produces noise that won't be bothersome since it is intended for use when the kitchen is already noisy.

You can find TEQOYA E500 right now on our website. Don't hesitate to contact us to find out more and get all the advice you need to get rid of kitchen smells and improve indoor air quality!

V - Sources

1- According to the Global Centre for Clean Air Research (GCARE), indoor air pollution generated by cooking fuels such as charcoal and wood causes around 4 million deaths worldwide every year.

2- See full report: Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures, American Chemical Society, 2020: https://pubs.acs.org/doi/10.1021/acs.est.0c00740 or the articles based on it: A hidden source of air pollution? Your daily household, February 2019: https://www.sciencedaily.com/releases/2019/02/190217115857.htm and The Hidden Air Pollution in Our Homes, department of public health, April 2019 https://www.newyorker.com/magazine/2019/04/08/the-hidden-air-pollution-in-our-homes

3- Ultrafine particles and PM2.5 generated from cooking in homes. Atmospheric Environment, 2011. https://www.infona.pl/resource/bwmeta1.element.elsevier-d1f9c262-a5c1-3095-8e6d-77aa496ccd35

4- Source apportionment of indoor PM2.5 and PM10 in homes. Indoor and Built Environment, 2020

5- Emissions and indoor concentrations of particulate matter and its specific chemical components from cooking: A review. Atmospheric Environment, 2013.

6 - Gruenwald, T.; Seals, B.A.; Knibbs, L.D.; Hosgood, H.D., III. Population Attributable Fraction of Gas Stoves and Childhood Asthma in the United States.Int. J. Environ. Res. Public Health 2023, 20, 75. https://doi.org/10.3390/ijerph20010075 Int. J. Environ. Res. Public Health 2023, 20, 75. https://doi.org/10.3390/ijerph20010075

7- TNO Report 2023, Health effects in EU and UK from cooking on gas, https://www.tno.nl/en/sustainable/safe-sustainable-living-environment/energy-built-environment/monitoring-energy-performance/indoor-particulate-matter/

8- Indoor Air Quality: Residential Cooking Exposures, State of California, Air Resources Board, 2001, https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/90689 and https://ww2.arb.ca.gov/resources/documents/indoor-air-pollution-cooking