How long do cars retain odors? The answer is blowin' in the wind

Dear Tom and Ray:

My problem began when I was driving down the road in our 2005 Dodge Caravan, packed full of our own kids and kids from the neighborhood. My elderly and ... let us call her "severe" mother was asleep in the front passenger seat when one of the neighborhood kids -- now a hero among his peers -- excreted certain organic gases, which announced themselves with a remarkably acute "crrrrraaaack." My severe, elderly and not very well-liked (by the kids) mother startled awake in her seat and said, "What?" This resulted in a tidal wave of elementary- and middle-school-aged hilarity. My kids now pay daily homage to the perpetrator of the pungent pontification -- he's a local hero, but that isn't my problem. Mom refuses to get back into the vehicle, claiming, "That awful thing is still loose in there." This is a problem, since she likes to attend each and every yard sale within 50 miles and is even more unpleasant if she is denied that pleasure. I have accused Mom of being vengeful about the children laughing. She denies this and claims there is a good, valid reason for her refusal to re-enter the vehicle. What I need is an authoritative statement on whether it's possible that the "awful thing is still loose" in the vehicle. Exactly how long is it justified for people to avoid a vehicle interior after such an incident? She thinks we need to get a new car!
-- Distraught Daughter in a Dodge

Ray: Gee, Distraught Daughter -- we'll call you D.D. -- I think this is largely psychological on Mom's part. She just doesn't want to ride with those little brats anymore.

Tom: I agree. I mean, even if that "awful thing" was a magnitude nine or 10 on the WindBreak Scale, it would still dissipate in a matter of minutes. Certainly within an hour.

Ray: I take it she hasn't refused to enter your living room, where your husband, no doubt, watches TV from the same spot on the sofa night after night and has his way with that poor foam cushion.

Tom: Cars have ventilation systems to bring fresh air into the passenger compartment. So, air is always circulating. And even with the vents off, cars are not airtight. If you put a car in water, it will sink. So it's nearly impossible for that particular collection of nitrogen, hydrogen, methane and hydrogen sulfide to still be inside your vehicle.

Ray: Unless, of course, it was more than just "wind" this kid released. But let's not go there.

Tom: It's also possible that Mom is smelling something else. You could have mold spores in your air-conditioning ducts, or one of those little brats could have spilled some milk and not told you about it. So you might want to ask an impartial nasal observer (call the Nasal Observatory) to take a ride with you and offer an honest opinion.

Ray: But even if you get a clean bill of smell, for the sake of family unity, I'd have the car detailed, D.D. That'll cost you about $100, but it includes a very thorough cleaning of the inside of the car. Tell them you want the seats and carpets shampooed, and ask them to use a "heavy hand" with the pine-tree air freshener. That way, Mom will know immediately that something has been done.

Tom: Then tell her you've had the car fumigated and you've called the kid's mother and had his diet changed, and that if she's willing to ride shotgun again, you'll take her to a yard sale nearby with lots of military surplus items, including gas masks. Good luck.

(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk Web site.)