What standalone actually buys you
A standalone unit is independent of the building. It needs a socket and nothing else, which means no landlord approval, no facilities coordination, no fit-out window, and no capital conversation. For leased retail, for a site that needs to be live this week, or for a trial before a group-wide rollout, that independence is worth more than the technical advantages of integration.
The limit is physics. A point source produces a gradient — strongest near the unit, weakest at the far wall. Under about 300 m² that gradient is imperceptible. Above it, people notice.
What integration buys you
A duct-mounted system uses the building's own air movement as its distribution network, so fragrance enters upstream of every supply diffuser. Intensity is even in the atrium and in the far corner of the top floor, which is the thing point-source units cannot guarantee at scale.
It also enables airflow-metered dosing: output tracks actual air volume rather than elapsed time, so a quiet Tuesday and a full Saturday deliver the same perceived intensity instead of the same volume of oil. Over a year that is a material difference in consumption.
The honest decision rule
If you control the HVAC and the space is over 500 m², integrate. If you do not control the HVAC, or the space is under 300 m², or you need it running before the next quarter, go standalone.
Between 300 and 500 m², or in a property with distinct zones, the answer is usually both: integration for the public volume, standalone units for the rooms that need their own identity.