Humans have a highly variable sensitivity to smell. No odour can be universally popular. Hence, there is a growing awareness that, ideally, interior spaces should be essentially odour-free.
If some activity in the room (which may merely be accommodating people!) Generates more or less unpleasant odours, it is highly desirable to remove them. Traditionally, such “removal” was achieved by simply masking the smell by dispersing incense or perfume in the space.
Products like FebreezeTM are more sophisticated: they contain cage molecules that entrap the odour molecules, thereby taking them out of circulation; they can no longer be perceived by the nose.
The most sophisticated approach is to actually destroy the molecules without introducing anything new into the atmosphere. This can be achieved by coating the interior surfaces of the room with a universal mineralizing agent. What is this? Most odours are due to volatile organic compounds (VOCs). If they were not volatile they would not be present in sufficient quantities in the atmosphere to be smelt. The VOCs are, therefore, circulating in the room and will from time to time collide with these interior surfaces. Since they are organic molecules, it will suffice to oxidize them to destruction — preferably all the way to CO2. Photocatalytic surfaces (PCS) can readily achieve this goal. They absorb light and convert it into oxidizing agents, which in turn then oxidize the VOCs that collide with the PCS. Being catalytic, once applied they should work indefinitely.