Kitchen extract fails for one of two reasons — the fan cannot hold pressure through the duct run, or nobody allowed for make-up air. BXF mixed-flow duct fans cover 290–2,200 m³/h and up to 693 Pa in six sizes from 100 to 315 mm, for cafe, restaurant, canteen and dishwash extract where the fan sits at the end of the run rather than in the wall.
Last updated: November 3, 2026
A commercial kitchen is the hardest ventilation job in a building: hot, greasy, humid, and squeezed into a duct route that was designed after the building was. This page covers what a ducted mixed-flow fan can and cannot do in a kitchen, how to size the extract and the make-up air that has to replace it, and which BXF model matches each space — so the fan you order still delivers its rated airflow once the filter, the elbows and the wall louvre are in the way.
Electric hobs, ovens, microwaves, coffee and tea stations, warming lines. Grease load is low, a stainless baffle filter sits at the hood, and the duct fan goes downstream at the discharge end. This is the case this page is written for.
Heavy frying puts far more grease into the duct. In the Middle East and Southeast Asia a duct fan on this duty is common practice, and it works when three things are right: a stainless baffle filter at the hood, the fan at the discharge end rather than above the cooking line, and an impeller that gets washed every season (the maintenance schedule sets the interval by grease load). Where the project is under a fire code that names a grease-rated fan, that code decides — send it to us and we will say what the installation needs.
In practice the difference is maintenance, not the fan. Grease that is allowed to build up on an impeller unbalances it, and an unbalanced impeller is what fails — not the motor size. Give the line a filter, a cleaning hatch and a fan you can reach without dismantling the duct, and a duct fan on a small restaurant kitchen runs for years. Airflow, pressure and duct velocity are calculated the same way in both cases, so the hood figures below apply either way.
MODEL MATCHINGReheat only, no frying. 8–10 air changes: BXF-150 (620 m³/h) for up to 70 m³, two units above that.
1,200–2,200 m³/h at 200–300 Pa: one BXF-315, or two BXF-200 in parallel if the duct route has several bends.
3,000–4,500 m³/h at 250–400 Pa: two BXF-315 in parallel into a common plenum. One unit alone will not hold this duty.
Steam and humidity, 15–20 air changes: BXF-200 or BXF-250, duct sloped back to a drain so condensate does not sit in the fan.
Heat and smell removal, 10–12 air changes: BXF-150 or BXF-200, mounted at the opposite end of the room from the door.
85% of the extract volume, introduced away from the hood face: BXF-250 or BXF-315, with a filter box on the intake.
1. Hood length. Allow 100 CFM per linear foot of hood face for light duty, 200 for medium (grills, fryers under a filter), 300 for heavy. That is roughly 0.5 m/s face velocity, the figure most hood manufacturers publish.
2. Convert and add margin. 1 CFM = 1.7 m³/h. Add 20% for the baffle filter, the elbows and the wall louvre — a fan rated at 2,200 m³/h free-air does not deliver 2,200 through a greasy filter and three bends.
3. Replace 85% of it. Make-up air is not optional: with the kitchen sealed, the extract fan starves, airflow drops by a third or more, the hood stops capturing, doors become hard to open and gas appliances can backdraft.
8 ft × 200 CFM = 1,600 CFM = 2,715 m³/h. With the 20% allowance: 3,260 m³/h at roughly 250–350 Pa. Two BXF-250 in parallel give 3,600 m³/h at 488 Pa — the smallest pairing that still meets the duty. Make-up air at 85%: 2,770 m³/h, one BXF-315 plus one BXF-150, introduced low level on the far side of the room from the hood.
Velocity is airflow divided by duct area, and it decides noise, pressure loss and whether grease keeps moving. For a grease duct, 7.6–10 m/s (1,500–2,000 fpm) keeps deposits from settling. For general exhaust, 5–8 m/s is comfortable. At rated airflow:
| Model | Duct size (mm) | Rated airflow (m³/h) | Duct velocity (m/s) | Note |
|---|---|---|---|---|
| BXF-100 | Φ100 | 290 | 10.3 | Short runs only — audible at this velocity |
| BXF-125 | Φ125 | 420 | 9.5 | Inside the grease-duct band |
| BXF-150 | Φ150 | 620 | 9.8 | Canteen and prep room extract |
| BXF-200 | Φ200 | 1,200 | 10.6 | Upsize the duct one step on long runs |
| BXF-250 | Φ250 | 1,800 | 10.2 | Best pressure of the small sizes |
| BXF-315 | Φ315 | 2,200 | 7.8 | Sweet spot for kitchen duct runs |
Velocity at rated free-air airflow through a duct of the fan's own diameter. Every 100 mm step up in duct size drops velocity by roughly 40% and takes 10–20 dB(A) off the noise — if a run has to be quiet, use a larger duct and a reducer at the fan.
PRESSURECatalogue figures are free-air, at 0 Pa. A kitchen is never free-air. Add up the resistance before choosing the model:
| Component | Typical pressure loss |
|---|---|
| Stainless baffle grease filter | 50–100 Pa (more as it loads) |
| Wall louvre / outside hood | 30–50 Pa |
| Each 90° elbow | 15–25 Pa |
| Straight duct, per metre | 3–5 Pa |
| Flexible connector, each | 10 Pa |
Example: 6 m of duct (30 Pa) + 3 elbows (60 Pa) + filter (80 Pa) + louvre (40 Pa) = 210 Pa on top of what the hood itself needs. Choose the model whose curve still gives your airflow at that pressure — on the BXF range that usually means BXF-200 and up. Send the run drawing and we will pick the model for you.
MODEL RANGE| Model | Duct | Airflow | Airflow | Max static | Power | Noise | Pcs/ctn | CBM | G.W. |
|---|---|---|---|---|---|---|---|---|---|
| (mm) | (m³/h) | (CFM) | (Pa) | (W) | (dB A) | (pcs) | (m³) | (kg/ctn) | |
| BXF-100 | Φ100 | 290 | 171 | 150 | 48 | 28–31 | 6 | 0.101 | 11.20 |
| BXF-125 | Φ125 | 420 | 247 | 180 | 50 | 28–31 | 6 | 0.101 | 12.70 |
| BXF-150 | Φ150 | 620 | 365 | 300 | 60 | 28–32 | 6 | 0.119 | 15.45 |
| BXF-200 | Φ200 | 1,200 | 706 | 380 | 120 | 45–50 | 4 | 0.097 | 14.00 |
| BXF-250 | Φ250 | 1,800 | 1,060 | 488 | 200 | 54–60 | 1 | 0.043 | 7.35 |
| BXF-315 | Φ315 | 2,200 | 1,295 | 693 | 330 | 60–70 | 1 | 0.072 | 9.15 |
Rated at 220-240V / 50Hz, free inlet and free outlet. 60Hz versions for Saudi Arabia, UAE, Kuwait and Qatar, and 110V / 60Hz for North America, are produced to order. Net weight depends on winding and cable set — confirmed on the packing list per order.
INSTALLATIONA stainless baffle filter in the canopy, then the fan downstream and outside the cooking space. Never inside the canopy, never in a grease duct run.
Cleaning hatch before and after the fan. Even a filtered line coats the impeller over a season, and an unbalanced impeller is a warranty claim.
Two flexible sleeves and anti-vibration mounts if the fan hangs above a ceiling — this is what stops kitchen rumble reaching the dining room.
Fall the run back towards the hood or a drain point so condensate and cleaning water do not collect inside the fan.
Local isolator next to the fan for service. IP44 motor for washdown and dishwash extract areas.
Introduce low level on the opposite side of the room. Blowing supply across the hood face breaks capture and pushes grease into the room.
CE is standard — certificate XH2601E0321945GC (Xihua International Testing & Certification, Shenzhen), valid to 2031-01-28. The factory holds ISO 9001 (04625Q15304R1M) and CCC (2024010702612682). ETL can be arranged on request for US distribution; SAA for Australia is renewed per order and is not currently held. All numbers are published for you to verify on the certificate verification page.
Where they are made. Four workshops, 50,000 m² of production buildings, twelve injection machines and eight assembly lines in Shengzhou, Zhejiang — see the factory and capacity page.
BUYER FAQTell us the hood length, the cooking equipment under it, the duct length and bends, the voltage and the destination port. We reply with the airflow you need, the model that delivers it at that pressure, and a formal quote — within 24 hours.