We trust you voted first in item 1 of this newsletter and then recommend you read Dr. Charles B. Keil’s study titled Kitchen Hood Performance in Food Service Operations. Dr. Keil is an Associate Professor at Bowling Green State University in the Environmental Health Program. He and two colleagues, Dr. Hailu Kassa and Mr. Kenny Fent addressed two primary questions.

First, are the hoods meeting quantitative operating guidelines? Secondly, do qualitative inspections identify hoods that are not meeting the guidelines? You may be surprised by the results.

UP YOUR STACK™.com has been granted permission by the corresponding author and the editors of the Journal of Environmental Health to republish the report.

The article is well written and describes the process and results of visiting 60 individual restaurants with a total hood count of 89 units. The primary purpose of the study was to measure the flow rates of these hoods to determine if they meet certain commonly accepted guidelines. One of the primary purposes of the kitchen ventilation system is to control the risks of fumes from cooking processes. A second is to contain any fire outbreaks allowing the fire suppression system to put out the fire. Their results provide for an interesting study.

ACGIH and ASHRAE provided the criteria for the two air flow guidelines that were chosen to measure against. 39 percent of the hoods met ACGIH guidelines while only 24 percent met ASHRAE guidelines. Perhaps even more interesting is the fact that in less than 4 percent of the 89 hoods inspected, did sanitarians identify inadequate flow rates.

While that fact is interesting, we find it entirely believable. Believable that so few hoods were actually recognized as poor performers. After all, how is anyone including an inspecting sanitarian expected to recognize inadequate air flow unless smoke is blowing in their face. Even those of us who have spent a lifetime in the industry would find it impossible to walk up to a hood and say the hood is working properly. Or not!

Even with sophisticated testing gauges, there is often dispute involving the measurement of air flow. So much depends on factors that cannot be seen by the casual observer such as make-up or replacement air currents flowing through the space. Even doors opening and closing can have a major effect. People walking by are disruptive to the normal operation of any hood for a period of several seconds as they pass by. Four way ceiling diffusers near the hood are permanently disruptive to proper exhausting.

Is the duct system clean? Is the fan running at the proper speed to maintain design guidelines or is the belt broken? Did the cook just dump a full load of meat, chicken or ribs on the broiler or grill?

How can sanitarians or anyone else for that matter be expected to know when a hood is operating properly? How are they expected to know what air flow the hood was designed to operate at? Or what modifications may have been made since the original installation of the hood, the duct system or the make up air system? Or what operating adjustments building engineers or maintenance staff may have made over the course of time causing the system to operate below design criteria.

The newly accepted idea of using energy saving variable speed controls may only make it more difficult to judge proper operation as more of these smart systems come into use. These systems operate at lower speeds when there are no-load or limited cooking conditions present. At slow speeds it may be difficult to know the fan is running due to a lack of noise coming down through the ductwork.

Perhaps what is needed is a simple metering device mounted on the front of the hood. Existing hoods could be retrofitted. New standard hood systems without variable speed technology could be designed to include such a device. UP YOUR STACK™.com has discussed the idea of such a small device with one major manufacturer and designer of controls. The device would be mounted so that the inspector could readily see a meter that simply reads in a red or green zone when the fan is on.

If the needle is in the green zone, the hood is operating in a zone acceptable to meet the design guidelines. If the needle is in the red zone, it should be noted on the sanitarians inspection report and checked out by an HVAC serviceman capable of determining air flow.

Think about how easy it would be to monitor hood air flow with this approach. It would improve the quality of life for chefs and cooks everywhere. And for many other kitchen personnel within proximity to all cooking hoods.

It’s an idea to consider. Let us know if you think the idea has merit. If you are an UP YOUR STACK™.com member, post your thoughts on the Bulletin Board.