How Do I Scent a Large Waiting Area Without Making Seats Near the Diffuser Too Fragrant?

Treat it as a distribution problem, because that is what it is. A single point source does not fill a room to a level; it produces a gradient, strong within a metre or two of the nozzle and progressively thinner with distance and mixing. So the two facts your patients are reporting - the room is about right, and the near chairs are too much - are both true at once, and turning the output down until the near chairs are comfortable simply moves the problem to the far end, where there is now nothing. The fix, in order. First, move the source. Get it out of the seating zone entirely and into the room's air path: away from the chairs, out of the direct blast of a supply grille or air curtain, and somewhere in the travel toward a return or a corridor mouth, at roughly a metre above the floor and angled into open volume rather than across the front row. In most large waiting areas that means a side wall well away from the counter and away from the busiest bank of seats. That single move flattens more of the gradient than any change of setting will. Second, lower the output once the position is right, and accept a slightly quieter far end as the trade. Third, move the chairs if the layout allows - it is much easier to relocate two seats than to argue with the airflow, and the metre and a half immediately around a source should simply not be a place anybody sits for an hour. What you must not do is add a second source. Two units in one connected volume do not combine into even coverage; they create two overlapping gradients with a strong patch at each and an unpredictable middle, and you now have two settings, two refill intervals and two things to keep in step. One source per volume of air, never one per room. A second machine legitimately belongs to a second volume - a different floor, a wing on its own air handling, or an executive lounge behind a closed door - and nowhere else. The honest concession is that a long or L-shaped waiting area will always have a quiet end. That is acceptable, and chasing the last few metres of it is exactly what leads centres into buying the second unit that ruins the room. Everything behind the corridor stays unscented regardless. Fragrance here is an ambience decision like lighting, seating or signage, it sits alongside ventilation and cleaning rather than instead of them, SOSA products are not medical devices, and the clinician's judgement overrides any scenting plan.