September 2006 Edition
Clearing the Air - Ventilation is Imperative to Kitchen Safety

The ventilation system that begins above your cooking equipment with exhaust hoods and a filtration system, and continues through the ductwork and fire system to the fans up on the roof, is a world of its own. It clears the air and keeps the kitchen from overheating, but it’s also one of the most important safety features in your restaurant.


Cooking equipment categories range from light duty to medium duty, to heavy and extra-heavy duty. Each category requires appropriate ventilation and exhaust systems, and new cooking equipment may require exhaust upgrades.


“A very serious problem is people who try to put in wood-burning equipment, or what’s referred to as solid-fuel equipment: burning charcoal or wood,” says George Zawacki, who runs the Web site Up Your Stack ( It is important to understand the appropriate ventilation and exhaust systems for all equipment.


Solid fuel equipment requires a completely separate system, including separate ductwork, and different filters to catch embers and prevent them from passing into the exhaust system where they can ignite grease buildup. Wood-burning and charcoal equipment is considered extra-heavy duty.


Ventilation maintenance is an important safety element, and not an area in which foodservice operators should skimp, Zawacki says. “The reality is that the systems need to be inspected and or cleaned a minimum of every six months. The grease buildup, based on the types of cooking, can reach dangerous levels,” he says. Cooking methods such as heavy-duty broiling, high-fat meats, high-temperature cooking, and woks cause more grease buildup than other types.


Because ductwork maintenance is an overhead expense, it affects the bottom line. Managers who try to stretch the limits between cleanings may be courting disaster. Grease buildup in ductwork is a serious fire hazard.


Depending on volume and type of cooking, ducts may require more frequent maintenance than fire codes require. Some companies, including one of the major fast-food burger chains, mandate ductwork cleaning not on the basis of time, but by food volume.


“They know from history that once they’ve cooked a certain number of pounds of hamburger meat, those ducts are going to be coated with grease and particulates,” Zawacki says. “Whether that’s 60 days or 90 days or 120 days makes no difference. Most people in the business just have it in their heads that you’ve just got to do it every six months.”


Primary filters inside vent hoods are not as efficient at grease removal as they were once thought to be. Baffle filters were originally thought to be 90 to 95% effective, but modern testing equipment has proven them to be only 30 to 35% effective.

“Which means that instead of 5 or 10% of grease particulate getting through the filter into the ductwork, it’s really more like 65 or 70% is going through the system and basically depositing on the insides of the ductwork,” Zawacki says.


Newer solutions are in development that should provide more efficient primary filtering. One of the most promising is ultraviolet (UV) technology.

UV systems begin with traditional primary filters, which are now known to remove only the larger grease particulates as air passes through. Next, the air passes through a bank of ultraviolet bulbs. These bulbs cause a chemical reaction in the grease, changing the composition of the grease particulates into a fine grey powder.


The technology has been around for a while, but is still being improved, and Zawacki says many people remain wary of adopting it. Vancouver, B.C. is one of the areas leading the way.

“The Vancouver airport authority has recently mandated that only ultraviolet systems would be allowed for any new installations or remodelled installations from here on out,” Zawacki says.

While UV systems may eventually reduce duct-cleaning costs, those savings are offset by added maintenance costs such as the UV bulbs, which last 800 to 1200 hours.


While there are many responsible duct-cleaning companies, there are also some that will offer a low price and do a poor job, Zawacki warns.


To do a good job in duct cleaning takes a team effort. It shuts down everything for hours. All the wastewater has to be collected. It’s a big job.

If speed and price seem too good to be true, it is recommended that you take a flashlight and have a good look up into the ductwork to make sure the job has been done right.


“The key element is safety,” he says.