InCar Air Quality – PM2.5 & VOCs

Long posts need short summaries:

  • Indoor air can be up to 5x more polluted than outdoor air (EPA, 2017)
  • Filtration systems are a great solution to prevent outdoor pollutants from entering the car
  • InCar Air Quality can still be bad due to VOCs developing inside the car
  • MEMS & air purifiers can be a solution to further improve the system and people’s health

In recent posts I already pointed out, that the indoor air quality (IAQ) in cars is as important as in your home. The often stressed ‘We spend 90% of our time indoors’ statement (cf. EPA, 2018) also includes the time you spend in vehicles. (cf. Klepeis et al, 2001) Cars already have a filtration system installed, but mostly it is not eliminating all hazardous compounds. Why ‘mostly? Because Elon Musk, CEO of Tesla, Inc., recently tweeted about the indoor air quality inside its Model X & S – and it is impressive.

The graph below shows the measurement conducted by Tesla with a Model X. They focused on PM2.5, short for particulate matter with a diameter of 2.5µm or smaller (cf. EPA, 2016). Tesla’s HEPA filtration system is able to clean the air within two minutes from extremely hazardous (in the test shown below ~1000µg/m³) to good air quality standards, reaching from 0 to 35µg/m³, according to EPA’s ‘Air Quality Index’ (cf. EPA, 2018).

Tesla_BWDM_air quality
Indoor Air Quality of Tesla Model X, tested with 1000µg/m³ of PM2.5 pollution, retrieved from:

PM2.5 isn’t everything

Now, this is amazing and a huge step forward to increase people’s health. But as you can see in the graph above, they focus on PM2.5. Don’t get me wrong – reducing the level of PM2.5 is important, especially when we talk about ‘InCar Air Quality’, but there is always a way to improve.

…of course, I’m talking about VOCs

Volatile Organic Compounds – gases caused by the human body, e.g. breath & body odours (cf. Shirasu & Touhara, 2011), car seats, the dashboard and other materials inside the car (cf. Brodzik et al, 2014). Especially when materials inside the car heat up due to the sun, the VOC level increases (cf. Greenguard, 2006). Being exposed to those gases can result in headaches, dizziness and fatigue (cf. EPA, 2017) – distractive symptoms while driving (even with Telsa’s autopilot).

‘That New-Car-Smell is so great!’ – Uhhm…no it’s not

…at least not for your health. I conducted a air quality measurement to show you what I mean. Below, you see a graph, measuring the VOC level inside a brand new car. Bosch Sensortec provided me one of its BME680 gas sensors which does exactly that and displays the data with their developed ‘Index for Air Quality’. The value ‘0’ means ‘good indoor air quality’ – the value ‘500’ means ‘poor air quality’ and is in fact the maximum which can be displayed. If the Index for Air Quality exceeds the value of 351, Bosch Sensortec suggests three main steps as protective measures:


car measurement new design
‘New-Car-Smell’ VOC measurement, conducted with Bosch Sensortec’s BME680 IAQ sensor

What you see here are VOCs being expelled by the materials inside the car. Among others, these include formaldehyde & benzene which can be dangerous in high amounts (cf. Greenguard, 2006). Click here to download a list of additional gases found by the Greenguard study cited.

So, the measurement, supported by the mentioned scientific study, shows that a main portion of the overall ‘InCar Air Quality’ actually develops inside the car – no matter how good your filtration system is, air quality is still bad. However, of course filtration systems help to reduce air pollution inside automobiles caused by bad outdoor air, affecting the driver’s and passengers’ health. But it does not automatically mean that the pollution problem is solved.

The Greenguard study is suggesting that car manufacturers should use ‘[…] low-emitting, non toxic materials […]’ (Greenguard, 2006) – until then, customers should air out their vehicles and open the windows for two to six months. (cf. Greenguard, 2006) Now, this doesn’t sound like a convenient solution to me, but it is certainly better than being exposed to the potential danger and its possible consequences.

So, here is a suggestion to Tesla and all other car manufacturers:

Implement an air purifier into your future automobiles – or even better: Offer it as an option to past models and install it as a mandatory feature in future models PLUS the filtration system! In this way, it is possible to eliminate PM2.5 AND VOCs, both affecting people’s health.

‘Filters are giant, […]’

– Elon Musk

If filters are giant, use something insanely small!

Concerning the tweet of Mr. Musk – I might have a solution.

If the filtration system is too big for certain models:

  • Use an IAQ MEMS gas sensor (~3x3mm) for detecting VOCs and monitoring IAQ
  • Use a PM2.5 sensor for particle detection
  • Implement an air purifier to let the device take immediate action & improve the air quality inside the car
  • Save battery & reduce power consumption, by purifying the air only when the sensors exceed a certain level of pollution (e.g. EPA IAQ index)


The awareness for the importance of Indoor Air Quality needs to be raised! With your voice and actions, things can change!


Thanks for reading!
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Brodzik, K., Faber, J., Łomankiewicz, D. & Gołda-Kopek, A. (2014). Journal of Environmental Sciences: In-vehicle VOCs composition of unconditioned, newly produced cars. 26(5), pp.1052-1061,

Klepeis, N.E. (2001). Journal of Exposure Analysis and Environmental Epidemiology: The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. 11, pp. 231–252, doi:10.1038/sj.jea.7500165

Shirasu, M., Touhara, K. (2011). The Journal of Biochemistry: The scent of disease: volatile organic compounds of the human body related to disease and disorder. 150(3), pp. 257–266,


Greenguard Environmental Institute. (2006). A Study of IAQ in Automobile Cabin Interiors, GG Publications, Inc., retrieved from:

Uniform Resource Locators

Bosch Sensortec GmbH, BME680, retrieved from:

Bosch Sensortec GmbH, Home, retrieved from:

Environmental Protection Agency. EPA’s Report on the Environment (ROE), retrieved from:

Environmental Protection Agency. The Inside Story: A Guide to Indoor Air Quality, retrieved from:

Environmental Protection Agency. Particulate Matter (PM) Pollution, retrieved from:

Environmental Protection Agency. Volatile Organic Compounds’ Impact on Indoor Air Quality, retireved from:

Environmental Protection Agency. What is the Air Quality Index for Health?, retrieved from:

Tesla. Putting the Tesla HEPA Filter and Bioweapon Defense Mode to the Test, retrieved from: