Why does the fog smell?

Why does the fog smell?

short answer: because some gasses and dirt gets dissolved in water

explanation:Before I answer this question, I would like to clarify that fog does not smell by default, but just in some specific cases. Now lets have a closer look at the formation and the composition of Fog.

Fog start forming close to ground when there is a combination of high humidity and relatively cold temperature (2.5-4°C). In these conditions, water vapour starts condensing on fine dust particles and other aerosols in the air. Condensed water droplets start growing until they reach some balance with surrounding air. So far good, hardly any smell.

Now we need to take into account that fog often forms in stale weather. Forming fog stops various dust and gasses from escaping from ground further away. Some of gasses and dust particles also got dissolved in the water droplets. If you are close to a city or a farm, various pollutants and aromatic substances get transported to you dissolved inside water droplets of fog. When you breath, your smell receptors in nose catches these small droplet and you smell something.