# That "wet road" smell when it rains... **URL:** \ **Category:** Factual Questions\ **Created:** [December 11, 2003, 4:23pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376 "2003-12-11T16:23:21Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [December 11, 2003, 4:23pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/1 "2003-12-11T16:23:21Z")
You know that distinctive smell you get when the first rain shower after a long, hot, dry spell hits asphalt? Does anyone know what compound(s) is/are responsible for it, and why they only seem to get released in these circumstances? I love this smell, but you don’t get to experience it very often! ---
**Author:** ![TheJungOnes](https://avatars.discourse-cdn.com/v4/letter/t/cab0a1/32.png) [@TheJungOnes](https://boards.straightdope.com/u/TheJungOnes)\ **Post date:** [December 11, 2003, 4:35pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/2 "2003-12-11T16:35:32Z")
[http://www.mit.edu/~goodmanj/madsci/897083302.Ch.r.html](http://www.mit.edu/~goodmanj/madsci/897083302.Ch.r.html) This page talks about the smell: "So what is that smell produced by wet concrete? I honestly don’t know, but It’s similar to the smell of freshly-mixed concrete, and I’ve also smelled it when carrying out the reaction Ca(OH)2 + CO2 -\> CaCO3 + H2O Some rocks (limestone?) also smell like this when wet. I suspect the smell has something to do with calcium; either small particles are released into the air which enter your nose, or there’s some sort of gaseous calcium-containing molecule produced by interaction between carbon dioxide, water, and a calcium compound (though that seems unlikely.) " ---
**Author:** ![Flash-57](https://avatars.discourse-cdn.com/v4/letter/f/839c29/32.png) [@Flash-57](https://boards.straightdope.com/u/Flash-57)\ **Post date:** [December 11, 2003, 7:35pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/3 "2003-12-11T19:35:27Z")
I’ve always been led to believe that the smell is from the accumulation of oil, gasoline, dirt, pulverized rubber, and whatever has fallen on the road since it last rained. When it does finally rain, all those nasty smells are kicked into the air for you to sniff. If it rains hard, or has rained recently, you won’t get that smell because all the oils and crap will have already washed away. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [December 11, 2003, 7:47pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/4 "2003-12-11T19:47:47Z")
I love that smell. My nose tells me it’s motor oil and dust. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 11, 2003, 9:04pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/5 "2003-12-11T21:04:04Z")
I always heard it was bacteria spores. [www.howstuffworks.com](http://www.howstuffworks.com/question479.htm) ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [December 11, 2003, 11:34pm UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/6 "2003-12-11T23:34:40Z")
No, that’s the kind of “rain in your garden” smell. This is what I’m talking about (from that site)… > [@](#): > > Because of chemicals in the atmosphere, rainwater tends to be somewhat acidic, especially in urban environments. When it comes in contact with organic debris or chemicals on the ground, it can cause some particularly aromatic reactions. It breaks apart soil and releases minerals trapped inside, and it reacts with chemicals, such as gasoline, giving them a stronger smell. These reactions generally produce more unpleasant smells than bacteria spores, which is why the after-the-rain smell isn’t always a good one. So, I guess it’s acid rain reacting with petrochemicals… Yum! ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [December 12, 2003, 4:48am UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/7 "2003-12-12T04:48:27Z")
> [@](#): > > \*Originally posted by r\_k \* > \*\*No, that’s the kind of “rain in your garden” smell. > > This is what I’m talking about (from that site)… > > So, I guess it’s acid rain reacting with petrochemicals… Yum! \*\* Yyeeeaaaahh! That’s what I’m talkin’ about! Whooooo! Some say you shouldn’t pet the sweaty chemicals. Durn fools.😛 ---
**Author:** ![Rhum\_Runner](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@Rhum\_Runner](https://boards.straightdope.com/u/Rhum_Runner)\ **Post date:** [December 12, 2003, 5:20am UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/8 "2003-12-12T05:20:43Z")
You smell that? Do you smell that? …Napalm, son. Nothing else in the world smells like that. I love the smell of napalm in the morning…The smell, you know that gasoline smell, the whole hill. Smelled like…victory. ---
**Author:** ![hyjyljyj](https://avatars.discourse-cdn.com/v4/letter/h/0ea827/32.png) [@hyjyljyj](https://boards.straightdope.com/u/hyjyljyj)\ **Post date:** [December 12, 2003, 7:56am UTC](https://boards.straightdope.com/t/that-wet-road-smell-when-it-rains/218376/9 "2003-12-12T07:56:14Z")
I thought I was the only one who liked that smell. Reminds me of playing street hockey when it would start to drizzle. Those last few desperate minutes of playing before you had to quit were the childhood sublimity equivalent of those last few minutes of sleep before the real buzzer goes off…