What is "out-gassing" and is it dangerous?

Dear Car Talk

Dear Car Talk | May 01, 2001

Dear Tom and Ray:

What is the film that develops on the inside of my car windows? It's especially bad on the front windshield. I used to think it was cigarette smoke, but I quit that filthy habit. Any clues? -- Clint

RAY: It's probably tiny, microscopic pieces of your car's interior, Clint. The plastic and vinyl in your car actually evaporate or "sublimate" over time. It's called out-gassing.

TOM: My brother does something called out-gassing, too, but we have him on a strict Beano regimen for that.

RAY: Out-gassing of plastic, vinyl, glue and other petroleum-based products is actually a serious problem. I mean, sure, it gets all over the inside of your windows. But what about the inside of your lungs? Formaldehyde, one of the products of out-gassing, is an irritant over the short term, but it might cause serious respiratory problems over the long term.

TOM: To give you an idea of what you're breathing, a recent study by a Japanese public-health institute found that the interior of a representative test vehicle contained formaldehyde and 113 other potentially harmful, volatile organic compounds.

RAY: The study also found that the out-gassing was at its worst when the car was brand-new -- when the emissions exceeded World Health Organization indoor air-quality standards by up to 45 times. Then, after about five months, the emissions dissipated to almost nothing. Sounds good, right? But the vapor levels then rose again during the summer months, when the weather got warm.

TOM: There is one other possibility in your case, Clint. You might have a leaky heat exchanger (aka heater core). If the heat exchanger is leaking a small amount of coolant, it could be distributed onto the windshield when the defroster is on. If you wipe a little bit off the windshield and smell it, coolant would have a slightly sweet odor.

RAY: So if it smells sweet, have your mechanic check the heater core. And if not, open your windows more often, especially during the summer months. And look on the bright side -- your car's interior might be carcinogenic ... but at least it looks good.

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