Capturing Cooking Effluent with the Exhaust Hood

Q: I’m having issues with my exhaust hood not catching all the discharge from my cooking equipment in the restaurant I just took over from a failed operator. Any ideas?

Exhaust Hood End Panels

Illustration of partial (top drawing) and full (bottom drawing) side panels. Used with permission. From Design Guide 1: Improving Commercial Kitchen Ventilation System Performance, Selecting & Sizing Exhaust Hoods

A: Issues involving exhaust hoods can be complicated and expensive. Start with the easy things first:

Check the fan to be sure it is operating. If the fan has a belt, also make sure the belt is in place.

Make sure the filters are clean and in place.

Ensure you have the proper overhang on the hood beyond the cooking equipment. The current code states that the hood must overhang the cooking surface a minimum of 6 inches.

Make sure there are no cross drafts from fans used to cool the staff or from diffusers in the ceiling for heating/air conditioning supplies. Cross drafts from diffusers, even those located many feet away from the hood, can have adverse effects on capture.

Experiment with side (or end) panels. Old cardboard boxes make great temporary trial capture improvers. Start by placing a sheet of cardboard at each end of the hood forming a partial end panel on the hood. Blocking off just 25-50% of the ends of the hood can make dramatic changes in capture along the front of the hood. If the temporary fix works, have the ends fabricated out of stainless steel and install them in place of the cardboard.

If all this fails consider hiring an expert to evaluate the situation. Hood design has advanced very rapidly recently and the new designs save energy and work better. Pay back can be more rapid than with other energy saving improvements so it is work the investment to hire a knowledgeable professional and budget for the best system for your circumstances.