Where should the Electrostatic Precipitator (ESP) be placed: near the hood or near the fan?

Standard guidelines for the installation location of kitchen exhaust purifiers: I. Optimal Solution:

Install near the exhaust hood (after a short, straight duct section from the hood outlet), in the sequence of Purifier → Fan. Key reasons:

**Highest purification efficiency due to high fume temperature and un-condensed grease**

Fumes exiting the hood are hot, with grease present as gaseous droplets or mist. If they pass through a long duct first, the grease condenses and adheres to the inner walls, forming thick, heavy deposits; this drastically increases the load on the purifier and creates a risk of short-circuits or fires.

**Protects the fan and significantly reduces cleaning and maintenance costs**

By passing fumes through the purifier first, the vast majority of grease is captured; clean air then enters the fan, leaving the impeller and housing virtually free of grease and eliminating the risk of fire caused by grease accumulation.

**Less grease in the ductwork and lower fire risk**

Only purified air flows through the ducts, resulting in very slow grease accumulation on the walls and making it easier to pass annual fire safety inspections.

**Installation spacing requirements:** Install the purifier after a straight duct section of 0.5–1 meter from the hood outlet. This prevents turbulent airflow from the hood from directly impacting the purification plates, ensuring uniform airflow. II. Not Recommended: Installing the purifier downstream of the fan (Fan → Purifier). Disadvantages:

The entire duct section is filled with high-concentration fumes, leading to rapid grease buildup on the walls and creating a severe fire hazard;

The fan directly inhales unpurified, concentrated fumes, causing heavy grease adhesion on the impeller; this disrupts the fan's dynamic balance and increases noise, while long-term exposure to hot, greasy deposits creates a risk of ignition;

The fan creates negative pressure, making the purifier prone to internal airflow short-circuiting; some fumes bypass the purification zone and are exhausted directly, resulting in substandard purification and a high likelihood of failing environmental compliance tests. III. Supplementary Notes for Special Operating Conditions

**Limited space; inability to install the purifier directly beneath the hood**

The upstream ductwork may be shortened to position the unit as close to the hood as possible; installing the purifier at the end of an excessively long exhaust duct is prohibited.

**High negative pressure from centrifugal fans; excessively long ductwork**

The purifier must be installed upstream; fire dampers must be installed in the ductwork, and regular duct cleaning is required.

**Specific requirements for electrostatic precipitators (ESPs)**

Electrostatic units are susceptible to damage from high-volume liquid oil droplet impingement; it is recommended to install a flow-equalizing screen or oil baffle at the hood outlet before the air enters the purifier.

**Concise summary of integrated engineering, environmental, and fire safety standards:

** Install the Fume Purifier (ESP) close to the hood. Sequence: Hood → Fire Damper → Fume Purifier (ESP) → Fan → High-level Discharge Duct.

DR. AIRE Electrostatic Precipiotator comes with UL listed, CE, RoHS, ASHRAE 52.2-2017 certificates. We help our clients/agents all over the world to set up business! Contact us for free quote now!

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