Technical
HVAC scenting vs AHU scenting: what is the difference?
Same principle, different injection point. The plant you already have usually decides which one you get.
Short answer
HVAC scenting injects fragrance into the ductwork of a building's heating, ventilation and air conditioning system, so scent is carried with conditioned air to whichever zones that duct serves. AHU scenting places the diffuser at the air handling unit itself — upstream of the duct network — so every zone fed by that unit receives the same fragrance from one point. AHU integration suits single-plant buildings; duct-level HVAC injection suits buildings that need different scents or intensities in different zones.
Where the diffuser physically sits
In an AHU installation the diffusion unit is mounted at or immediately downstream of the air handling unit in the plant room, dosing the supply air before it is distributed. In a duct-level HVAC installation the unit is fitted into a branch of the duct network serving a defined area.
Both keep hardware out of the occupied space. The difference is how far upstream you are, and therefore how many zones one unit can influence.
- AHU: one injection point, whole-plant coverage, simplest servicing
- Duct-level HVAC: one point per branch, zone-by-zone control
- Both are dry-vapour cold-air diffusion — no heat, no residue in the duct
How to tell which your building needs
If a single air handling unit serves the areas you want scented and you want one consistent character throughout, AHU integration is normally the cleaner answer. If the same plant serves areas that must smell different — a spa and a gym, a restaurant and a lobby — duct-level injection or separate standalone units give you that separation.
Where plant access is restricted, ducts are inaccessible above finished ceilings, or airflow is too low to carry vapour reliably, we will say so and recommend standalone units instead.
- Single AHU, one desired scent → AHU integration
- Shared plant, different scents by area → duct-level or standalone
- No usable ventilation, or a single room → standalone diffuser
What it costs and what has to be checked
Both routes are priced the same on our published rate card: £799 ex VAT outright, or £99 per month billed annually, covering up to 1,000m² with fragrance, servicing and support included. Above 1,000m² or across multiple zones, the specification is quoted per zone.
Before we specify anything we check airflow rates and velocities, duct layout and access, ceiling heights and treated volume, zoning, operating hours, and how scenting will interact with any BMS control already in place.
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FAQs
Related questions
- Does HVAC or AHU scenting leave residue in the ductwork?
- No. The oil is atomised into a dry vapour rather than heated or aerosolised, so there is no oily film left on duct walls, filters or diffusers.
- Can we scent one floor and not another?
- Where those floors are on separate zones or separate plant, yes. Where they share a single supply, you would need duct-level injection on the branch, or a standalone unit in the area you want treated.
- Will it interfere with our BMS or filtration?
- It should not. Diffusion equipment runs independently and is scheduled to your operating hours; we confirm filtration and control arrangements during the technical assessment before specifying.
- How long does installation take?
- Typically under two hours for a single injection point on accessible plant, carried out around occupancy and commissioned the same visit.
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