New-car smell: what you're breathing inside a car, and what helps

Some people love it. But “new-car smell” isn’t the smell of newness. It’s the smell of dashboards, seat foam, carpets, glues and fabrics releasing chemicals into a small sealed box that bakes in the sun.

This piece covers what’s been measured in car cabins, where the flame retardants come from, what the rules say, and the few things that make a measurable difference. For the plastic your car sheds onto the road, see our tyres article.

What new-car smell is

A Japanese team followed one new car for more than three years. They identified 162 organic compounds in its cabin air. The day after delivery, total VOCs were about 14 mg/m³, mostly hydrocarbons such as decane, undecane and xylene. By the next summer, levels were about a tenth of that. They kept falling with time, but rose whenever the cabin got hot.

German researchers who went looking specifically for the compounds you can smell found 41 potent odorants in two new cars, from esters and aldehydes to pyrazines.

Heat turns it up

The single most consistent finding in cabin-air research is that temperature drives emissions.

• In a new car parked for seven summer days in China, the temperature of interior surfaces, which reached 64.2°C, was the most important factor in VOC levels, more than the air temperature. Formaldehyde was the highest of 12 VOCs measured, and 15 of 40 measurements (37.5%) were above China’s guideline limit of 100 µg/m³.
• A Swedish lab study of 18 potential hormone-disrupting chemicals found average levels in cabin air at 80°C were 18 to 16,000 times higher than at 25°C, depending on the chemical. Several of the co-authors work for Volvo Cars.
• In new cars parked in sunshine, Chinese researchers found higher levels and more kinds of VOCs than in a climate-controlled test chamber, but after a period of driving, levels fell back to chamber levels.

These are small studies, some on a single car. But they point the same way, and match what’s known about mattress foam: warmth pushes chemicals out of materials faster.

Flame retardants in seat foam

The largest study of car flame retardants we found comes from Duke University. Owners of 101 recent US cars (the study recruited model year 2015 or newer) hung a silicone sampler on their rear-view mirror for a week. A chlorinated organophosphate flame retardant, TCIPP, turned up in 99% of vehicles.

• Seat foam is a source. About half the owners sent in a piece of seat foam: flame retardants were in 33 of 52 samples, TCIPP in 23. Cars with TCIPP in the foam had about 4 times higher median TCIPP in their cabin air in winter and about 9 times higher in summer.
• Summer is worse. In the 54 cars sampled again in summer, flame-retardant levels were 2 to 5 times higher than in winter, tracking outdoor temperature.
• It isn’t only the seats. Cars without TCIPP in their foam still had it in the air. The authors point to other foam parts such as headrests, plus plastics and textiles, as likely extra sources.

Should you worry about TCIPP? The authors note a 2023 US National Toxicology Program report found evidence it causes cancer in rats and mice. Its chemical cousin TDCIPP was added to California’s Prop 65 list in 2011, and the authors suggest that listing led to a switch from one to the other. That’s animal evidence, not proof of harm in people. A broader review by flame-retardant researchers concluded that organophosphate flame retardants raise health concerns at current exposure levels.

Commuting time seems to matter. Among students in Southern California who wore silicone wristbands for five days, TDCIPP was the one flame retardant whose levels rose with time spent commuting.

There’s one hopeful sign. Child car seats, which contain foam too, showed a significant decrease in flame retardants in Duke’s 2014 to 2016 screening.

Why your car has flame retardants

Because of a fire-safety rule written in the 1970s. The US standard FMVSS 302 says seat cushions, headliners, door panels, floor coverings and other interior materials must not burn faster than 102 mm a minute in a lab flame test. Its stated purpose is to protect occupants from fires started by things like matches or cigarettes.

The rule doesn’t require chemicals. But the Duke team says it remains the same as when it was introduced in the 1970s and is likely met with added flame retardants. Given the exposure they measured and what they call uncertain fire-safety benefits, they concluded that FMVSS 302 should be re-evaluated, the way California rewrote its furniture rule in 2013 so it could be met without flame retardants.

How much does it matter for your health?

Honestly: nobody knows, because nobody has followed drivers and measured health outcomes linked to cabin chemicals.

The closest is a risk estimate. Pooling published measurements, two California toxicologists estimated that benzene and formaldehyde were the only chemicals likely to exceed California’s Prop 65 safety levels in car air, for commutes of 20 minutes or more under higher-exposure assumptions. Benzene is mostly a traffic problem: in a Taiwanese driving study it came mainly from outside the car, while formaldehyde, acetone and ethanol came mainly from inside.

Cars carry plastic particles too. A French team measured a median of 2,238 microplastic particles per cubic metre in two cars, against 528 in apartments. Our dust explainer covers what that does and doesn’t mean.

What ventilation and shade actually do

This is the part with practical evidence, and the advice is consistent.

Ventilation helps a lot. In the Swedish study, several chemicals were below detection limits with the ventilation running. The authors recommend airing a warm car before you get in and keeping the fan on while driving. Driving with ventilation also brought VOCs back down to chamber levels in the Chinese study.

But outside air isn’t always clean. In heavy traffic, fresh-air mode and open windows let in exhaust. The Taiwanese study found they raised cabin particles and some VOCs, while recirculation kept particles out but ventilated so poorly that carbon dioxide passed 4,000 ppm. On a congested road, there’s a genuine trade-off. On an open road, fresh air wins.

Shade lowers the temperature, which should lower emissions. In Arizona, cars parked in full shade averaged 39.5°C inside, against 47.6°C in the sun. Nobody has measured chemicals in that exact comparison, but given how strongly emissions track temperature, the Duke authors suggest that parking in a garage or shade may limit flame-retardant release.

Air fresheners add to the problem. In a Korean test, one minute of spray freshener sent total VOCs up to 364 µg/m³ at the front seat. Recirculation kept those VOCs in the cabin. Outside-air mode cut them to about 56% of other modes.

The rules on cabin air (as of November 2026)

• United States. The federal rule that governs car interiors, FMVSS 302, is about flammability only. We found no US federal limit on chemicals in cabin air.
• China. GB/T 27630-2011, a guideline for assessing air quality in passenger cars, sets cabin-air limits including 100 µg/m³ for formaldehyde and 50 µg/m³ for acetaldehyde. China’s national standards register lists the 2011 version as current and recommended rather than mandatory.

Regulating what goes into the air is one route. The other, which the flame-retardant researchers argue for, is changing the fire rule so chemicals don’t need to go into the seats in the first place.

What you can do

Ranked roughly by how good the evidence is:

1. Ventilate, especially when the car is hot (good evidence). Open the windows or run the fan on outside air for a minute or two before you set off. Several chemicals fell below detection with ventilation on.
2. Park in shade or a garage (good evidence on temperature, inferred for chemicals). Shade kept cabins about 8°C cooler in Arizona, and heat is the strongest driver of emissions. A windscreen sunshade follows the same logic, though we found no study of it.
3. Use recirculation wisely. On congested roads it keeps exhaust out; elsewhere, outside air dilutes what the interior gives off. The Taiwanese study found you can’t have both at once.
4. Skip the air freshener (good evidence it adds VOCs). It raises VOCs and particles to cover a smell that ventilation removes.
5. Give a new car time. Emissions fall a lot in the first year: to about a tenth after a year in the one car followed for years. A used car has already done much of its off-gassing.

None of this touches the flame retardants built into the seats. That fix belongs to regulators and carmakers, starting with a 1970s fire test that researchers say needs a second look. For what LPP would want disclosed before calling any product a better choice, see our standards.

Common questions

Do electric cars have fewer flame retardants?

In the Duke study, TCIPP levels in cabin air were about 6 times lower in electric cars than in petrol cars. But the electric cars were dominated by a few brands, and the authors say the difference may reflect brand rather than engine type. It’s not a reason to choose a car.

Does the smell going away mean the chemicals have gone?

Not necessarily. In the one car followed for three years, total VOCs still exceeded an indoor guideline every summer. And flame retardants don’t announce themselves: in Duke’s study of 101 recent cars, TCIPP was in 99% of cabins and rose in summer, whatever the car smelled like.