Why Correct Duct Design Is Critical to ESP Performance in Commercial Kitchens

Electrostatic precipitator (ESP) units are widely used in commercial kitchen extraction systems to remove grease, smoke and airborne particulates. However, even the most advanced ESP unit will underperform if the ductwork feeding it is incorrectly designed.

In commercial kitchens, ESP performance is not just about the unit itself — it is fundamentally linked to duct velocities, airflow stability, and compliant duct transitions. Poor duct design can “suffocate” airflow, increase pressure losses, and significantly reduce filtration efficiency.

Duct Velocity: Getting the Balance Right

Ductwork must be designed to handle the required airflow while maintaining appropriate air velocities. If velocities are too high, air passes through the system too quickly, reducing the effectiveness of the ESP. If velocities are too low, grease and particulates can settle within the ductwork, increasing fire risk and maintenance requirements.

Correct duct sizing ensures stable airflow through the ESP unit, consistent face velocity across the electrostatic cells, and effective particulate charging and collection. Duct velocities should always be calculated based on the required kitchen extract volume, rather than forcing airflow through undersized ductwork.

The Impact of Poor Transitions and Reducers

One of the most common issues seen on site is poorly designed duct connections to ESP units. Sharp reducers, abrupt transitions, or non-compliant duct fittings can severely restrict airflow and create turbulence upstream of the ESP.

All ductwork connections, transitions and reducers should be designed and manufactured in accordance with DW144 standards. Properly formed reducers allow airflow to transition smoothly, preventing pressure drops and uneven air distribution across the ESP cells.

Avoiding Airflow Restriction (“Suffocation”)

When ductwork is undersized or poorly adapted, the system effectively becomes choked. This restriction reduces airflow through the entire extraction system, impacting capture efficiency at the canopy, ESP filtration performance, and fan duty and lifespan.

Straight Duct Requirements Around ESP Units

ESP units perform best when airflow entering the unit is stable and evenly distributed. Excessive bends, offsets, or dampers immediately upstream or downstream of the ESP can introduce turbulence and uneven velocities.

Where possible, straight duct runs should be provided before and after the ESP unit to allow airflow to stabilise. This helps maximise dwell time within the ESP cells and ensures consistent grease and particulate removal.

Designing for Performance from Canopy to Discharge

A successful commercial kitchen filtration system must be considered as a whole. From canopy capture through to final discharge, ductwork design plays a critical role in system efficiency, safety, and long-term reliability.

By ensuring correct duct velocities, DW144-compliant transitions, and adequate straight duct runs, ESP units can perform as intended — delivering effective filtration and supporting a cleaner, safer kitchen environment.