A kitchen extract terminal should discharge contaminated air where it can disperse without re-entering the same building or causing odour, grease and noise problems for neighbouring receptors.
Installation boundary: This article explains design and coordination principles. Drainage, ventilation, fire, electrical and fabrication work must be designed and carried out by competent people using current project documents, manufacturer instructions and the requirements that apply in the relevant UK nation.
The short answer
The correct terminal is project-specific. Local planning guidance commonly favours a high-level, vertically upward, unobstructed discharge located away from windows, doors, terraces and fresh-air intakes. Exact height and efflux conditions should come from the odour and dispersion assessment and any planning condition—not a universal 'one metre above eaves' rule copied from another council. The terminal must also be structurally supported, weathered, cleanable and safely accessible.
Assess receptors in three dimensions
Mark every opening and occupied area within and around the site: upper-floor flats, offices, roof terraces, dormers, hotel rooms, school yards, adjacent rooflights and mechanical air intakes. A receptor that is distant on plan may sit directly above a low-level terminal. Consider future permissions and the prevailing building geometry; a courtyard or gap between rear additions can trap odour even when the duct points away from the nearest window.
Fresh-air re-entry is not only a neighbour issue. A discharge near the kitchen's own make-up-air intake can return grease and odour to the room, contaminate filters and create a recirculation loop. Show both extract and intake on roof plans and elevations, with levels and separation, before planning submission.
Terminal form affects real performance
A cap or weather cowl can deflect the plume sideways or add resistance. Many planning guides therefore seek an unobstructed vertical discharge, sometimes with a high efflux velocity or engineered terminal. The fan and duct must be designed for that terminal resistance, and rain management should not create an internal grease sump.
Where high-level discharge cannot be achieved, better odour treatment may reduce risk but does not automatically make a poor terminal acceptable. Use the risk logic in an EMAQ+ odour assessment and the treatment options in commercial kitchen odour-control systems.
What common failures reveal
| Site symptom | Likely installation issue | Practical consequence |
|---|---|---|
| Odour enters upstairs windows | Terminal below receptor or plume trapped by facade | Complaints and statutory nuisance risk |
| Make-up filters become greasy | Extract terminal recirculates into intake | Poor air quality and maintenance cost |
| System flow is below design | Restrictive cap added after fan selection | Canopy capture failure |
| Roof stains around terminal | Low velocity, side discharge or grease carryover | Visual impact and roof damage |
| Terminal cannot be serviced | No safe roof access or isolation | Fan and discharge deteriorate unchecked |
Installation and coordination checklist
- Plot all sensitive receptors and air intakes in plan and elevation.
- Use the relevant local planning guidance and odour-risk evidence.
- Prefer an unobstructed vertical discharge where the project assessment requires it.
- Include terminal resistance in fan selection and commissioning.
- Prevent rain management details from trapping grease inside the duct.
- Coordinate structural supports, roof penetrations and waterproofing.
- Provide safe access for cleaning, fan work and inspection.
- Build the approved terminal height and form exactly as shown in the submission.
Commissioning and handover
Photograph the terminal from relevant surrounding viewpoints and record its final level, direction and distance from nearby openings and intakes. Commission airflow with the final terminal fitted. Include planning-condition evidence, fan data, roof-access instructions and the cleaning method for the discharge section in the operation and maintenance file.
Questions to ask before approving the work
- Which receptor controls the terminal location?
- What does the local authority or odour assessment require?
- Could the plume re-enter any air intake?
- Has terminal resistance been included in fan duty?
- Can the roof section be cleaned and serviced safely?
Capture the installation detail before it becomes a site problem
Plan the full kitchen installation across equipment, utilities, ventilation, safety, hygiene and handover.
Technical sources and further reading
- Westminster Council: Guidelines for kitchen extract ventilation systems
- Spelthorne Borough Council: Planning guidance for kitchen extraction systems
- HSE CAIS10: Ventilation of kitchens in catering establishments
Last technical review: 14 August 2026. Always check the latest manufacturer instructions, statutory guidance, standards and project approvals before installation.