`Sizing a scent system: how coverage numbers actually work`
Coverage figures on a spec sheet describe an empty box, not your lobby. Here is how ceiling height, air changes and door traffic move the real number — and how to sanity-check a proposal before you sign it.
What the spec sheet number means
Every diffuser is rated for a coverage volume, and that rating is measured in conditions your building does not have: a sealed room, still air, a standard ceiling. It is a useful comparison between units. It is not a plan.
Three variables move the real figure, and only one of them is on the sheet. Ceiling height changes the volume outright. Air changes per hour decide how fast the scent leaves. Door traffic decides how much of it is felt at all. Fragrance load itself is bounded separately by IFRA guidance.
Ceiling height is a multiplier, not a footnote
Coverage is quoted in square feet because that is what a floor plan shows, but diffusion is volumetric. A 2,000 sq ft lobby at 10 ft is a different job from the same floor plate at 22 ft — roughly twice the air to condition, and the upper volume does nothing for a guest standing at the desk.
"This is a quote"
Indicative planning bands
Use these as a starting point for a walkthrough, not as a quote. Real sizing comes off a site survey.
| Space | Floor area | Ceiling | Typical units |
|---|---|---|---|
| Boutique lobby | Up to 1,500 sq ft | Under 12 ft | 1 |
If a proposal quotes unit count without asking your ceiling height or your HVAC run schedule, it was priced off a floor plan. Ask for the volumetric working before you compare it to anything else.
Where perceived intensity actually lands
Doubling the fragrance load does not double what a guest notices. Perception compresses. Past a point you are spending on consumable and getting complaints, not presence.
Perceived intensity vs fragrance load
The most common fix on a service visit is turning the system down.
Sanity-checking a proposal
Four questions. If a vendor cannot answer all four, the number is a guess.
What ceiling height was assumed? What is the HVAC run schedule? Is the unit on the supply side or the return? What happens to coverage when the doors are propped open in the evening?
Sizing done properly is unglamorous — a tape measure, a run schedule and a walk through the space at the hour that matters. It is also the difference between a system nobody mentions and one everybody does.
