Since so many parts of the US (mainly the Great Plains, mid-west, and parts of the northeast) are experiencing normal interior Alaska winter temperatures right now, I thought I’d write about what/if we smell when it gets cold.
Our ability to smell things is related to temperature because temperature is a key factor in volatility (tendency to vaporize). We tend to smell volatile compounds (those with high vapor pressure at normal temperatures) that have molecular weights below 300 daltons. Volatiles with lower molecular mass tend to have lower boiling points and evaporate and diffuse more rapidly than compounds with high molecular masses. For example, ethanol (pure alcohol) has a mass of 46 daltons and will vaporize and diffuse at a lower temperature and more rapidly than indole (a fecal smelling element often added to jasmine perfumes to produce a musky scent) which has a mass of 117 daltons.
Boiling is one end of the vaporization extreme and freezing is the other. The freezing point of water is 0 but other molecules have lower thresholds–however, even if a molecule isn’t frozen, the colder it is, the less thermal energy it will have and its volatility will be reduced (think of how the aroma of cooled food is not as strong when it was hot). When temperatures are extremely cold, the sense of smell is de facto eliminated (even if your nose weren’t blocked by anti-frostbite protective gear like balaclavas). During the winter in Fairbanks, the only things you can reliably smell outside (down to a certain temperature) are wood burning stoves and car exhaust pollution–both in heavy concentrations trapped close to the ground due to temperature inversion. Maybe another reason we like hot bevvies during cold weather is the welcome rush of volatiles!