Short answer
The source must be tackled first when the odour indicates an active technical, hygiene or safety problem. Think of leaks, active mould, sewer gases, accumulated waste, insufficient extraction, a burning smell or unknown chemical emissions.
Odour is sometimes a warning signal
Not every unpleasant odour is just a comfort problem. A burning smell can indicate overheating. A strong sewer odour can signal a technical defect. A musty smell can go hand in hand with moisture.
In such situations, adding perfume before the cause has been investigated is the wrong order.
With moisture: dry and repair
EPA guidelines on mould are clear that moisture control is key. Leaks must be repaired and water-damaged materials must be dried, cleaned or, if necessary, removed.
As long as the moisture source remains active, a scent product cannot solve the underlying problem.
With ventilation: improve air quality
When kitchen, sanitary or material odours build up due to insufficient air renewal, it makes more sense to improve ventilation and extraction first.
Scent marketing should come on top of a well-functioning indoor environment.
When can odour control run in parallel?
Sometimes the cause is known and a repair process has started, but the definitive solution takes time. Think of municipal sewer works, drying out after water damage or a planned renovation.
If the space can be used safely from a technical point of view, temporary odour control can be deployed in parallel to limit the nuisance.
When can scent marketing simply start?
When there is no technical odour problem and the goal is brand experience, atmosphere or recognition, there is of course no source problem that needs to be solved first.
The distinction between scent marketing and malodour management must therefore be clear from the very first conversation.