Why do materials, weather and places have smells?

Volatile emissions inside new vehicles (VERIFIED): In new vehicles parked in sunshine, interior materials released higher concentrations and more kinds of volatile organic compounds than in a test chamber, including alkanes, alcohols, ketones, benzenes, alkenes, aldehydes, esters and naphthalene, and the levels fell to chamber levels after a period of driving. Scope: New vehicles of three brands; it measures emissions, not odour, and levels varied with model, speed, ventilation and temperature.

Old-book aroma and paper degradation volatiles (VERIFIED): Research on historic paper has measured volatile organic compounds released during material degradation and linked those emissions to the characteristic smell of old books. Scope: Supports the role of paper degradation volatiles; individual books and libraries can differ by materials, storage and environment.

Volatiles from line-dried laundry (VERIFIED): Cotton towels rinsed in pure water and dried outdoors in sunlight released C5–C9 oxidised compounds, including aldehydes such as pentanal, hexanal, heptanal, octanal and nonanal, which were not observed after drying indoors or outdoors without sunlight. Scope: Detergent-free cotton towels analysed without olfactometry; that sunlit surface photochemistry produces the smell is the authors' proposal.

Petrichor and rain on dry ground (VERIFIED): The scientific literature has used the term petrichor for the characteristic earthy odour associated with rain acting on dry mineral and soil environments. Scope: Historical scientific framing of petrichor; this does not mean every rainy environment has one identical chemical profile.

Phenolic odorants in hardwood smoke (VERIFIED): A gas chromatography–olfactometry study of condensed mixed-hardwood smoke found phenolic compounds such as guaiacol, 4-methylguaiacol and 4-methylsyringol among its most potent odorants, alongside compounds such as 2,3-butanedione. Scope: Supports the odorants of one condensed hardwood smoke studied for food smoking; open fires, other woods and burning conditions can differ.

1. Next time it rains after a dry spell, step outside and describe the smell before and after the first minutes of rain.

Smell and Science is free, like all of SmellBook Learn. It covers where smells come from: the volatile compounds behind them and how researchers find the ones that matter. Every finding is a VERIFIED claim shown with its scope. It is not medical or safety advice. Lessons on smell receptors, perception and adaptation will be added when registered sources support them.