Capturing the cooking plume and replacing exhaust air are one system problem.
The hood exhaust fan draws the rising heat, vapour and grease-laden plume into the capture zone. Make-up air replaces the air leaving the kitchen, but its direction and quantity must support capture instead of blowing the plume out of the hood.
Follow the airflow through the equipment.
Plume
Cooking appliances produce a rising stream of heat, moisture and contaminants.
Capture
The hood creates a capture region that guides the plume toward filters and the exhaust duct.
Exhaust
A fan overcomes filter, duct, fitting and discharge resistance to remove the captured air.
Make-up air
A separate supply replaces exhaust air without creating a cross-draft through the plume.
What the fan is responsible for
- Maintain the hood exhaust duty at the installed filter and duct resistance.
- Provide replacement air that supports kitchen pressure balance and capture.
- Operate with the required interlocks, controls, cleaning and fire-protection sequence.
Why the route matters
- Too little replacement air can depressurize the kitchen and disturb the designed flow.
- A high-velocity make-up jet aimed at the hood can push the plume into the room.
- Grease accumulation changes resistance and creates a cleaning and fire-safety issue.
Define these inputs before choosing a fan
A LONGWELL route to evaluate: square-housing centrifugal duct fans for clean make-up air
LONGWELL square-housing centrifugal duct fans are a pressure-capable candidate only for the filtered, clean make-up-air side. Select the duty from the required replacement airflow and the total resistance of the louver, filter, damper and duct, then check temperature, power, controls, mounting and service access. The grease-laden exhaust path is a separate duty and is not offered from this evidence.
Verify the complete equipment, not the fan in isolation
Send the hood exhaust and clean make-up-air designs separately.
Share both paths so the pressure balance can be checked. LONGWELL can review a clean make-up-air duct-fan candidate after its airflow, resistance, temperature, controls and approval boundary are defined; this page does not offer a grease-exhaust fan.