What causes new car smell? You won’t believe your nose…

It’s one of those most gorgeous smells: the lingering musk of the brand-new car. It’s one of the joys of shopping for a new car, even if you’re just hopping in and out of models on the showroom floor, huffing the pristine interiors

It’s so good that you can even buy scented candles that replicate it – but what actually causes new cars to smell of new cars? We’ve been investigating and we’ve unearthed a few surprises – and not particularly good ones at that…

Admit it – you can almost smell the cow

New car smell all comes down to a single word: outgassing. That’s not the type of outgassing that gives used cars a different kind of smell or a curry house loo a recognisable pong, but a chemical process that occurs during the curing of materials and when the material is subject to changes in temperature.

The biggest culprit is the thermoplastics that form the majority of cars’ interior trim panels.

Bentley owners may cry “there are no plastics in my car”, but even in luxury cars the nice and tactile surfaces presented to the cabin occupants are usually backed by a plastic of some kind that attaches to the car’s structure. Depending on the car, there may be as much as 10% plastic by weight crammed inside it – largely in the cabin.

As well as the plastic itself, the solvents and plasticisers used to make the plastics easier to work with can be retained by the material and evaporate over time in a similar manner.

A deep breath in…

There are plenty of other synthetic materials in a vehicle that emit smell similarly. Look down at the carpets or up at the headlining – particularly if you’ve opted for a slightly plush motor – for example. These are made with the same mix of organic materials and solvents to retain the dyes used to colour them.

Painted interior trim panels outgas too as a consequence of the colouring process and many interior materials are coated with flame retardants that will also contribute. Leather and, more commonly, leather-like materials used in higher grade models also have their role to play in new car smell.

… and out…

Smells like… what did you just say?

OK, so we know that the smell is caused by materials curing and letting out gases. But what exactly are the gases that leak from your new car?

Well, it’s not terrific news. Most odours come from a family of chemicals called “volatile organic compounds” (VOCs) – and very few things that start with the world ‘volatile’ are good.

For the most part these are complex hydrocarbons – the same sort of basic molecules that you’ll find in petrol and oil – mixed in with halogens like chlorine or bromine. If you think that doesn’t sound like a good thing to be sniffing in, you’d be right. Many of the chemicals in question have been implicated in ‘sick building syndrome’, a phenomenon where occupants of a building share unspecific poor health (headaches, tiredness, itchiness) without any obvious cause.

Of course it’s called ‘new car smell’ because it only exists in new cars. The initial outgassing is extremely rapid and levels of these chemicals in the cabin air falls to almost undetectable amounts after just a couple of weeks – but may rise again on warm days in the first few months.

Isn’t this a bad thing?

Car manufacturers are changing how they make interior trim to rely more on water-based solvents and glues in order to address any potential health problems that new car smell may cause. Michigan-based environmental health concern Ecology Center regularly tests American-market new cars for air quality and publishes its results year on year – with Honda and Toyota regularly putting in a good showing for the healthiest interiors.

Honda: manufacturer of the safest new-car smell

I smell a conclusion…

So although new car smell is right up there with coffee grounds, fresh bread and bacon for the best smells in the world, as usual it turns out that what we like may not be all that good for us. As manufacturers seek to change their cars for the healthier, it may be an endangered scent too – get your fix while you can!

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