A device that captures the scent of surrounding air by sucking it through a specialized filter. The filter is designed to absorb and retain scents.
Currently, the only effective method to capture airborne scents is headspace technology, but it's only used to capture scents present in a headspace of an odorous object, like a flower, not the lingering scent of the environment.
"Record" smells of different environments.
Invoke memories of a specific place by smelling a sample of its' scent.
Know how a certain place smelled at a particular time, during a significant event there (a concert, a gathering, filming of the movie, etc.) even if you haven't been there (a scent sample could be sold and shipped to you, this provides a business opportunity).
Monitor how the smell in a particular place changes as time passes, e.g. place a device in a meadow and "record" the smells of different seasons.
Would be useful for olfactory research, e.g. testing of this hypothesis.
A proposed device is simply an air pump with a specialized, scent retaining filter covering the air inlet. A device would be similar to a filter-based collector of atmospheric aerosols. Just, in this case, the filter would be designed to capture scents (volatile compounds) instead of particulate matter.
The optimal airflow for best capturing of air scents should be determined in advance as well as the optimal time of absorption. The pump turns off automatically after the intended time is reached.
A piece of fabric of a particular composition and thickness could work as a filter.
A simple proof that air scents can be captured on fabrics is the fact that our clothes absorb and retain environmental scents. After walking outside your cotton scarf or a woolen jacket often smells like outside air for a while. In the same way your clothes can also retain the smell of indoor environments you often spend time in. If fabrics can absorb scents lingering in the air just by being kept in that environment for a while, passing an airflow created by an air pump through them should intensify the absorption/retention of smells.
Filters should be sterile (autoclaved or otherwise sterilized not to let microorganisms multiply and their metabolism products contaminate the smell of the sample). Fabrics used to absorb unpleasant odours could potentially work for making such filters, I suppose they are good for absorbing any odour, not just unpleasant ones. The filter itself should have no or minimal smell of its own.
New filters would be kept in tightly sealed plastic bags to prevent premature scent contamination. After collecting environmental scent, the filter would be placed in the same bag from which it was taken, the bag would prevent the collected scent from fading as well as prevent the filter from attracting additional scents from environment.
The user takes the new filter out of the bag (preferably with the tweezers or gloves), opens the device, puts it in a dedicated frame, closes the device, and starts the air pump.
Such an air pump with insertable scent collecting filters could possibly be made small enough for anyone willing to carry in their backpack and collect scents whenever they go. All you'd need is to change filters and store them in a specialized case, this would take some space and perhaps remind a case of a professional photo camera.
Because such a filter-based scent capture method wouldn't aim to recreate the molecular composition of a certain scent, only to capture the whim of the general air scent, it would be enough trying filters of different compositions and seeing how reminiscent the captured scent is to that lingering in the air that was pumped through the filter. This could be done by comparing the two scents using only the human nose.