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Learn · Part One — Learning to smell · Lesson 10 of 10

What new car smell is, and whether it is harmful

New car smell is dozens of volatile compounds from plastic, glue and leather. It peaks when the car is new, hot and closed up — and falls quickly if you ventilate the right way.

Get into a brand-new car, shut the door and breathe in: plastic, leather, glue, and a sweetish layer that is hard to name. That is the new car smell. It is not one smell but a sum — dozens of volatile organic compounds escaping together from materials that have only just left the factory.

Where it comes from

A car interior is plastic, foam, adhesive, leather or imitation leather, fabric and paint. Every new material still holds some solvent, plasticiser and additive that has not yet evaporated, and these escape into the air a little at a time. The process is called off-gassing.

Measurements in new cars usually find two large groups: hydrocarbons — alkanes and aromatics such as toluene, xylene, ethylbenzene and styrene — and aldehydes, led by formaldehyde and acetaldehyde. A 2022 study of cars from three manufacturers found alkanes and aromatic hydrocarbons made up most of it.

Three things decide the concentration

The age of the car. Off-gassing is strongest while the materials are new, then falls away. A 2000 study measured total volatile organic compounds in one new vehicle at about 7,500 µg/m³ on the first day — roughly a hundred times the level outdoors — and found it about 90% lower after three weeks. What remains keeps falling slowly for months.

Temperature. Sun heats the materials and makes them off-gas faster. In the 2022 study, cars parked in the sun reached cabin temperatures of about 29 to 62 °C, and concentrations were clearly higher than when the same cars stood in a test chamber at 25 °C. At 25 °C all eight compounds tested were within their limits; in the sun, formaldehyde in one car reached about 7.8 times its limit. A 2023 study found that concentrations follow the surface temperature of the interior materials more closely than the air temperature — a dashboard in the sun is a large source.

Ventilation. With the doors shut and the air conditioning on recirculation, the compounds build up. Once the car is moving with outside air coming in, concentrations fall quickly: for some of the cars in the 2022 study, levels after 60–90 minutes of driving were close to those in the test chamber.

So is it harmful?

The short answer: it depends on the dose, and the highest doses fall exactly when they are easiest to avoid.

Some compounds in new car smell are classified carcinogens: formaldehyde and benzene are in Group 1 of the International Agency for Research on Cancer (IARC), and acetaldehyde is in Group 2B. At the levels usually found in cars, the most common short-term effects are stinging eyes, a sore throat, headache and nausea, more noticeable in sensitive people and young children. The long-term risk comes from breathing it repeatedly for many hours, not from getting into the car once.

The 2023 study sampled the air in a new SUV parked outdoors for 12 days, with the cabin temperature ranging from 21 to 63 °C. The researchers identified 20 compounds coming from the car's materials; at times formaldehyde exceeded the Chinese standard by up to 35% and acetaldehyde by up to 61%. China is one of the few countries with a standard specifically for the air inside cars (GB/T 27630); its draft revision sets limits of 0.10 mg/m³ for formaldehyde and 0.06 mg/m³ for benzene.

None of this means a new car is toxic. It means the first few weeks are the time to ventilate on purpose.

What to do in the first weeks

  1. Open the doors for a few minutes before getting into a car that has been in the sun. Hot air trapped in the cabin is when concentrations peak.
  2. Drive with outside air, not recirculation, and open a window when you can.
  3. Park in the shade and use a windscreen shade. Cooler materials off-gas more slowly.
  4. Don't rely on your nose. After a few minutes in the car, your nose stops reporting the smell — that is olfactory adaptation — but the compounds are still there. No longer smelling it does not mean it has gone.

Don't use fragrance to cover new car smell

This is something we have to say plainly, even though we sell fragrance.

Essential oils and perfumes are volatile organic compounds too. Adding another source of scent to the cabin does not make formaldehyde disappear; it only stops you noticing the new car smell. More than that, many components of essential oils — limonene in citrus, alpha-pinene in pine — react with ozone in the air and form formaldehyde themselves. A 2006 study of household products containing terpenes found formaldehyde was the main by-product when ozone was present.

So the right order is: ventilate until the new car smell has clearly faded over the first few weeks, then add the scent you want — lightly, and hung well away from the plastic and leather of the interior.

Sources

  • Grabbs, Corsi and Torres (2000). Volatile Organic Compounds in New Automobiles: Screening Assessment. Journal of Environmental Engineering.
  • Guo et al. (2022). Evaluation of Typical Volatile Organic Compounds Levels in New Vehicles under Static and Driving Conditions. International Journal of Environmental Research and Public Health 19(12), 7048.
  • Wang et al. (2023). Observation, prediction, and risk assessment of volatile organic compounds in a vehicle cabin environment. Cell Reports Physical Science, 101375.
  • Destaillats et al. (2006). Indoor Secondary Pollutants from Household Product Emissions in the Presence of Ozone: A Bench-Scale Chamber Study. Environmental Science & Technology 40.

Further reading for this part

A shared list for the whole of Part One — Learning to smell, not a note for every sentence. We state what each source was used for.

  1. Asifa Majid and Niclas Burenhult, 2014. Odors are expressible in language, as long as you speak the right one A study of the Jahai of the Malay Peninsula, a group with an abstract smell vocabulary. It underpins the central argument of Part One: the gap lies in vocabulary, not in the nose.
  2. Caroline Bushdid et al., 2014. Humans can discriminate more than 1 trillion olfactory stimuli The trillion figure is widely quoted. We cite it together with its critique, because Meister (2015) and Gerkin and Castro (2015) showed problems with how it was extrapolated. It is our example of how an attractive number can spread without anyone checking it.
  3. Những cây thuốc và vị thuốc Việt Nam A Vietnamese-language source for the species names, parts used and sensory descriptions of most of the medicinal plants in the dictionary. Where it and other literature disagree — as with garden mint — we give both.

One thing must be said plainly. We have not read every work above in the original; most of the knowledge comes through secondary literature and reviews. We say so rather than let the list suggest a depth of research we have not reached.

Last updated: October 2026