Short answer
Odour nuisance arises when volatile substances from a source reach the air and are perceived at a concentration that is experienced as disturbing. In commercial buildings, drains and sewers, moisture, waste, sanitary facilities, kitchen processes, HVAC and materials are common sources.
Think in terms of source, route and receiver
A practical analysis looks at three elements.
Source: where are the odorous substances formed?
Route: how do they reach the public area - via air flows, pipe shafts, ventilation or porous materials?
Receiver: where and when do customers or employees experience the nuisance?
Without distinguishing these three, treatment often takes place in the wrong place.
Drains and sewers
A dry trap, defective connection, pressure problem or external sewer problem can cause sulphurous or other unpleasant odours. Because some sewer gases can also pose health and safety risks, a strong or unexplained sewer odour should be investigated technically and not simply covered up with perfume.
Moisture and mould
Musty odours can go hand in hand with moisture and microbial growth. Micro-organisms and water-damaged building materials can release volatile compounds.
That is why a persistent musty odour is a reason to look for leaks, condensation, water ingress and hidden damage.
Waste and organic sources
Food, rubbish, drains, grease and sanitary areas can cause odour nuisance when storage, cleaning or air renewal is insufficient.
HVAC as a distribution route
Sometimes the source is not where the odour is perceived most strongly. Ventilation can carry odour from one space to another.
That explains why simply adding perfume locally often does not help.
New materials
Paint, glue, floor coverings and furniture can release their own volatile substances during or after renovation. In that case, ventilation and product instructions come before scent marketing.
First diagnosis, then scent strategy
Only once the cause and route are clear can it be determined whether source repair, ventilation, cleaning, temporary odour control or a combination is needed.