Measured airflow. Recorded conditions.
Capture the brief, measure the site and prepare a design intent for review. This fictional survey records 27.5% of its stated airflow target with the faulty hallway smoke damper temporarily opened. The as-found operating flow is not established by those readings.
- Prepared by
- Aldon Project Consultants
- End client
- Northgate Logistics Group
- Site
- Unit 12, Ashfield Park, Meadow Lane, Northgate
- Survey date
- 22 April 2026 · BS EN 16798-1 Cat II
- Reference
- BTO-NLG-DSV-001
- Status
- For review
Illustrative example: fictional project and parties.
Capture the brief, then prove it on site
Aldon Project Consultants was instructed, acting for Northgate Logistics Group, to design sufficient fresh air into the canteen at Unit 12, Ashfield Park, and to assess two smoke dampers that were not operating. The Design Survey stage captures the brief, records the site with a measured survey, and prepares a review-ready report with a single buildable design intent for the firm's competent reviewer to approve. The skills prepare the draft; the technical reviewer validates and issues it.
The 0.248 cu m per second reading was taken with the hallway smoke damper temporarily opened, then returned to its found condition. It is not an as-found supply measurement. The stated 0.9 cu m per second design target and proposed design intent remain for competent technical review.
What the six diffusers actually deliver
In-situ air volumes were measured at each of the six canteen supply diffusers with a calibrated balometer hood. With the faulty hallway smoke damper temporarily opened, the readings total 247.6 L/s (rounded to 0.248 cu m per second). Against this example's stated 900 L/s target, that is 27.5%, rounded to one decimal place from the raw total. The recorded BS EN 16798-1 Category II basis for 75 people remains subject to technical review.
| Supply grille | Velocity, m/s | Flow, L/s | Damper |
|---|---|---|---|
| Grille 1 | 3.50 | 22.9 | Circular VCD |
| Grille 2 | 8.49 | 56.1 | No VCD fitted |
| Grille 3 | 6.63 | 43.8 | Rectangular VCD |
| Grille 4 | 4.86 | 31.9 | Circular VCD |
| Grille 5 | 8.01 | 52.9 | Rectangular VCD |
| Grille 6 | 6.08 | 40.0 | Rectangular VCD |
| Total measured, damper open | 247.6 | 27.5% of stated target |
Compare the readings, not a safe occupancy
The measured-open total gives 3.3 L/s per person at 75 people. The comparisons below use that temporary measurement condition and the example's stated 12 L/s-per-person target; they are not a safe-occupancy or compliance decision. About 30 people were observed at peak, with windows opened for cooling.
| Occupancy | L/s per person | Of stated target | Calculated comparison |
|---|---|---|---|
| 75, design peak | 3.3 | 27.5% | Below stated target |
| 40, busy | 6.2 | 52% | Below stated target |
| 30, observed | 8.3 | 69% | Below stated target |
| About 20 | 12.4 | 103% | Above stated target in measurement condition only |
The canteen smoke damper at the duct entry is operational, its magnet confirmed working. The hallway smoke damper near the clock-in is stuck closed and not re-magnetising, and was restricting airflow. It was opened for the measurements and returned to its found condition. It needs replacement. All other dampers are manual volume-control dampers for balancing.
The design intent, and what constrains it
The proposed design intent targets about 0.9 cu m per second of fresh air for the stated 75-person peak, with dedicated extract, supply reinstatement to the male WC and shower, and replacement of the faulty hallway smoke damper. This is for competent design review, not a verified design, completed repair or confirmation of compliance.
| Constraint | Effect on the design |
|---|---|
| 480 mm ceiling void | Limits duct routing for any new supply or extract |
| Layout differs from the 1995 drawing | Drawing 95-6816-M13 Rev C no longer matches; sections altered in later refurbishments |
| Shared air-handling control | All canteen ventilation runs from the office air-handling panel, accessed via a locked service corridor |
| Decommissioned kitchen ventilation | Kitchen supply and extract are capped but visible; not reusable as found |
Once reviewed, a survey can inform a subsequent design brief. This specimen remains For review. The linked Design Pack illustrates a separate canopy commission at Ashfield Park; it is not the next output of this canteen survey.