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April 2004

By Mike Sherer
SPECIAL REPORT: A Case Of De-Duct-ion

Ventless hood options multiply as more nontraditional locations haul in and hook up foodservice equipment.

The three keys to success for many operators—location, location, location—are leading to foodservice operations popping up in the most unlikely places. Quick-service operators, in particular, are shoehorning kitchens into gas stations, c-stores, shopping mall kiosks, corners of retail stores, and even churches.

As traditional sites have become harder to find, the demand for ventless cooking equipment keeps growing. Ventless hoods allow operators to take advantage of existing spaces without the cost of retrofitting them with ductwork and a permanent exhaust hood.

Applications where ventless equipment makes most sense include high-rise buildings, mall kiosks and c-stores. Even restaurants that have run out of space under existing hoods use ventless appliances when menu changes call for added equipment.

Originally considered a niche product focused primarily on fryers, ventless hoods are now found on a gamut of cooking equipment. While some are integrated into specific pieces of cooking equipment, a number of manufacturers now offer stand-alone hoods that can accommodate a variety of equipment configurations.

Though the technology for ventless hoods has been around for awhile, ventless equipment wasn’t developed until the 1980s. Early models were very expensive, costing up to $1,000 per linear foot, and hard to maintain.

Clearing The Air
The key to ventless equipment is the filtration system. The filters must be able to take enough grease and smoke out of the cooking effluent to exhaust clean air back into the cooking area. There are two basic types of filtration systems: mechanical and electronic.

All ventless hoods have the same type of baffles that traditional hoods use to extract large grease particles from the effluent coming off the cooking equipment. Mechanical filtration systems have additional filters that remove smaller particles. These can be constructed of different materials, and often there are two or more.

Common configurations include combinations of the following:
• Stainless mesh screen filters designed to remove smaller grease particles.
• Disposable paper or woven fiberglass filters which remove most of the smallest particles. These can include HEPA filters (see sidebar).
• Activated charcoal filters. Also disposable, these final filters are used to remove odors from the air before it is exhausted back into the space.

Electronic filtration is accomplished with an electrostatic precipitator. Air passing through this filter is electronically charged, and the charged grease and smoke particles are attracted to a collection grid with an opposite charge. While ESPs do a good job of cleaning the exhaust, most ventless systems using them also have a charcoal filter to help remove odors.

Safety Measures
Ventless hoods must meet certain safety standards to receive UL and NFPA listings. Beyond the typical specs that electric equipment must meet to attain listings, UL and NFPA standards focus on a couple of key areas. The first is fire safety.

All ventless hoods must have a fire suppression system built in. Most have a fusible link in the hood that melts and triggers the release of a wet chemical agent in the event of a fire. Some larger ventless fryers have an additional fusible link on the fry pot that trips the system when the oil temperature gets too hot before a fire can ignite. These systems also typically shut off the hood fan when tripped.

Some hoods come with fire suppression systems fully installed. Others come plumbed and wired, but you need to have them charged and tested by a local dealer after they’re installed. (Note: Oven applications do not require fire protection systems, but all other applications do.)

Other safety features, covered by UL standards, revolve around indoor air quality (see sidebar, page 34). All ventless equipment is designed with a safety interlock system that shuts off the hood and the cooking equipment if the filters either are too dirty to operate effectively or not installed properly. Stand-alone hoods have built-in electrical outlets with the same feature, so the interlock will work no matter what piece of equipment you plug in.

Keeping It Clean
Cleaning ventless hoods is essentially the same as cleaning a traditional hood. Stainless baffles and many pre-filters are safe to run through a dish machine and should be cleaned daily at the least.

Systems with disposable filters have pressure sensors that turn on a warning light when the filters need replacing. Filter life can range from four weeks to six months depending on the type and the cooking load.

Systems that use ESPs often include a soak tank for cleaning the air cleaner as standard equipment. Electronic air cleaners have to be cleaned daily, and may need more frequent cleaning depending on your cooking load.

The Other News
While ventless hoods make it possible for almost anyone to implement a hot food program, they do have drawbacks. The biggest of these are noise, heat and odor.

Because ventless hoods have to meet minimum air quality standards, their design incorporates powerful in-line fans capable of pulling airflow loads of anywhere from 1.5 to 6 in. of static pressure. And since those fans are right in the hood (which is usually in a public space) that means they’re pretty noisy. Even quiet hoods are typically 70 decibels or more.

There’s not a lot you can do about the noise. If you’re willing to go to extra expense, though, you can reduce the noise by ducting the hood’s exhaust up into a false ceiling (which sort of defeats the purpose).

Heat is another problem, both the radiant heat coming off the cooking equipment and the heat of the recirculated hood exhaust. Unlike a traditional hood, you don’t need to provide make-up air to a ventless hood. However, your HVAC system will have to provide additional cooling and recirculation to overcome the heat from the ventless system.

Most manufacturers recommend you plan on supplying the same airflow from your HVAC system that the hood requires to operate efficiently. So, if your hood operates at 400 cfm you’ll need an additional 400 cfm of recirculated air from your HVAC system. In some cases, that won’t be a simple matter of cranking up the HVAC a notch. It may require some new ductwork to redirect airflow in the space, adding to your initial cost.
Finally, while most ventless systems do their best to filter out cooking odors before air is exhausted back into the cooking space, it’s almost impossible to eliminate odors entirely. Here again, your HVAC may be called upon to help move more air through the space to dilute or remove odors.

On to the manufacturers. See the sidebars throughout this story for profiles of some of the ventless hood models on the market.

High Efficiency Particulate Arrestor filters were originally developed during World War II by Atomic Energy Commission scientists. The objective at the time was to find a way to filter radioactive particles out of the air.

To qualify as a HEPA, a filter must be able to capture 99.97% of all particles 0.3 microns or larger in size. To put that in perspective, smoke particles range in size from .01 to 1 micron. A human hair is about 70 to100 microns in width. Anything less than 10 microns can’t be seen by the naked eye.

HEPA filters can be made from any “dry media,” but most are folded paper (which provides lots of surface area) or woven fiberglass. They actually become more efficient as they get dirty, but they require fans capable of pulling high static pressures.—MS

In addition to the stand-alone hood makers, a number of companies have incorporated proprietary hood systems into their equipment lineups. Specifically, you can buy a variety of equipment from Alto-Shaam Inc. and Wells Mfg./Carrier that incorporate ventless hoods as an option. And two other companies, Auto Fry and Perfect Fry, produce fully enclosed, ventless frying systems.

Alto-Shaam now makes a couple pieces of equipment with ventless hoods. The AR-7VH is a factory-installed ventless hood on top of the company’s AR-7E electric rotisserie oven. The VHML-5 and VHML-10 hoods are available installed on a variety of Combitherm oven/steamers.

All three of the UL-listed ventless hoods use a two-stage filtration system—stainless baffles and disposable charcoal filter—to remove grease and odors from the cooking chamber. On Combitherm ovens, condensed steam drains through an opening in the rear of the hood. In the AR-7VH, condensed steam drains inside the rotisserie.

The ventless equipment has special timed door interlock switches that prevent the door from being opened until the steam and vapors are pulled into the hood. Both the AR-7VH and the VHML-5 pull 530 cfm through the filter system. The VHML-10, designed for use with larger Combitherm ovens, draws 1,200 cfm. To find out more, call Alto-Shaam at 800/558-8744, or visit www.alto-shaam.com.

Meanwhile, Wells Mfg., a leader in countertop cooking equipment, has designed several pieces of equipment as complete ventless systems. That means that the hood on each unit is specifically sized for the cooking equipment it’s attached to. The result, according to the company, is efficiency; most units operate at less than 400 cfm.

Equipment in the 18-product ventless line includes fryers, griddles, fryer/griddle combos, convection ovens and cooktops. All systems come with a safety interlock system that shuts down equipment and hood if air filters aren’t properly in place, and an Ansul R-102 automatic fire suppression system. Ventless fryers with capacities of 30 lbs. or more have a second fusible link on the fry pot which can detect runaway temperature conditions and trigger the fire suppression system before a fire even ignites.

An airflow sensing system warns you when it’s time to change the replaceable HEPA and charcoal filters. The units’ centrifugal baffles and pre-filters are both washable. Contact Wells at 800/777-0450 or visit www.wellsbloomfield.com.

Auto Fry, a product of Motion Technology, has offered fully enclosed, fully automated, deep-fat frying machines for some time, complete with integrated ventless hood and built-in Ansul fire suppression systems. You can choose from three counter and floor models that produce 20 to 120 lbs. of french fries per hour. Operation is simple: simply place food product in entry chutes, select fry time on keypads, and wait as food is fried and automatically delivered to receiving baskets. Internally, two filters clean grease-laden air. Auto Fry information is available at www.autofry.com or by calling 800/348-2976.

And Perfect Fry Co. offers a similar ventless, fully enclosed fryer in its PFC Series. Four countertop models—all with the same footprint—allow you to fry 30 to 60 lbs. of product per hour. Perfect Fry uses a HEPA filtration system, and the company says that during EPA 202 air emissions testing, results showed its filter allowed 0.039 mg/m3 of effluent into the air, well below the 5 mg/m3 limit. For information on Perfect Fry, visit www.perfectfry.com or call 800/265-7711.—MS and JH

One concern about ventless hoods is that sometimes what you don’t see is what you get. All ventless hoods must meet minimum indoor air quality standards to get a UL listing. Unfortunately, there’s a loophole in the standard that makes it difficult to compare one hood’s efficiency with another’s.

UL 197 basically says that a ventless hood (or any ventless equipment, like a countertop oven) can’t emit any more than 5 mg of particulate per cubic meter of air. (The actual standard is an average of 5 mg/m3 over an 8-hr. cooking period.) The problem is that the standard is based on a concentration, not an absolute quantity.

For example, 8 mg/m3 in an exhaust flow of 400 cfm can be cut in half to 4 mg/m3 if you increase your flow rate to 800 cfm. The same quantity of grease and smoke is produced, but you’ve diluted it. If your cooking equipment is producing 0.010 lb./hr. of grease, the concentration of particles in your exhaust at a flow rate of 500 cfm would be 5.3 mg/m3, higher than the UL 197 standard. Bump your flow rate up, and the concentration falls within standards.

How much grease you produce depends on what food you’re cooking and on what type of equipment. The new ASHRAE 154 standard spells out all those factors, which can help you tell if your ventless system is exhausting clean air or not. Even better, UL says it intends to revise the standard; it just isn’t sure when.—MS


In the late 1980s, Ballantyne Food Service Equipment developed a ventless hood for use with one of its pressure fryers. Well known for its fryers, pressure fryers, smokers and turn-key fried chicken program, the company saw an opportunity to penetrate new markets.

That first ventless hood used an electrostatic precipitator, which required strict maintenance on the operator’s part. In 1999, Ballantyne introduced its stand-alone hood to give operators greater flexibility. The unit uses mechanical filtration—stainless baffles, a mesh screen filter and activated charcoal filter—and can accommodate up to an 85-lb. capacity fryer.

Dual fans pull 900 cfm through the filters, allowing the unit to handle heavier cooking loads. Baffle and mesh screen filters are easy to clean in a warewasher, and the charcoal filter is replaceable. A safety interlock prevents the hood and equipment from operating if the filters are dirty or installed incorrectly. A warning light indicates when it’s time to change filters.

An Ansul wet chemical fire suppression system automatically discharges in the event of a fire, and can be manually triggered.

Contact Ballantyne for more information by calling 800/262-5016 or visiting www.ballantynefoodsvc.com.

BKI-Worldwide got its start as the Barbecue King Co., a restaurant in Greenville, S.C. The company’s founder invented a revolving barbecue oven in 1954, and over time, the company evolved into a manufacturer of a wide variety of foodservice equipment ranging from combi ovens and fryers to hot food merchandisers. Supermarkets and c-stores are strong niche markets for the company’s products.

BKI’s FH-28 freestanding ventless hood is designed to work with a variety of cooking appliances that comply with its UL listing. The hood accommodates fryers, griddles and sandwich grills, for example, but you’re limited in terms of the size of equipment you can use. The hood is just 31 in. wide, so only equipment that is no more than 28 in. wide will fit. The hood also requires an 18-in. clearance on each side from combustibles.

The hood features a patented control system, and an advanced two-stage filtration system removes grease particles. A signal light alerts you when the disposable filter needs changing, and a safety interlock shuts the hood and equipment off automatically if the filter gets too dirty. BKI recommends supplying at least 450 cfm of fresh air from your HVAC system for each hood.

The fully plumbed fire suppression system must be activated on-site by an authorized Kidde dealer.

For more information, contact BKI-Worldwide at 800/927-6887, or look the company up on the Web at www.bkideas.com.

In business since 1952, Giles makes a variety of foodservice equipment ranging from rotisserie ovens to fryers. The company makes several ventless fryers, but also makes ventless hoods designed for use with different appliances.

All of the ventless hoods and ventless fryers made by Giles use a three-step filtration process. First, stainless baffles extract large grease particles. An electrostatic precipitator cleans the air stream further, and a final charcoal filter helps remove odors.

The ventless hood line includes two freestanding fryer hoods, two oven hoods and two all-purpose hoods. One of the oven hoods, the OVH-10, is 36 in. wide and designed for use with convection ovens. The PO-VH is 60 in. and designed for conveyor ovens.

The two all-purpose hoods are 5 ft. and 6 ft., and work with a variety of equipment. Both are designed to be hung from the ceiling. Up to 40 kW of equipment can be arrayed under the larger hood. Depending on cooking load, the manufacturer
recommends up to 800 cfm of recirculated air from your HVAC system.

All the hoods in the line come with a soak tank for the electronic air cleaner. Baffle filters and the air cleaner should be cleaned daily. The disposable charcoal filter needs to be replaced about every 30 days.

Fire suppression is provided by an Ansul R-102A system. The units are piped and have conduit for routing a fusible link cable through the hood. Final installation, charging and testing should be done on-site by an Ansul dealer.

To find out more, contact Giles Enterprises at 800/554-4537, or go to www.gilesent.com.

Halton Co., a manufacturer on the cutting edge of UV-C light technology in its vented hoods, also makes a stand-alone ventless hood. Called the CanVent, the hood is available in four different sizes ranging from about 41⁄2 ft. to 10 ft. wide to accommodate a variety of equipment configurations. CanVent also is ETL listed for gas appliances, perhaps the only ventless hood in the industry approved for use with gas cooking equipment.

Halton claims the CanVent is more efficient than other hoods because its design facilitates greater capture and containment of cooking effluent. A front “air bar” directs the air stream above the cooking surface and up into the hood, reducing the need for high exhaust rates. Dishwasher-safe stainless baffles and a mesh screen filter extract large grease particles, and a replaceable HEPA filter helps eliminate small particles and odor.

The CanVent has a factory-installed automatic fire suppression system, and like all other UL-listed ventless hoods includes a safety interlock system that shuts down the hood and equipment in case of dirty filters or fire.

To learn more, get in touch with Halton Co. by calling 800/442-5866, or go to www.haltoncompany.com.

Well known for its vented hoods, including the new Reactocell using UV-C light technology, Vent Master/Enodis developed a ventless hood system some 10 years ago. Designed for specific limited applications, the Kiosk Ventilation System features a stand-alone hood and filtration system usable in a variety of configurations.

The system’s design has some unusual features. Hoods come in three widths—5 ft., 6 ft. and 8 ft.—mounted on a stainless backwall at a height of 6 ft. 2 in. A 3-ft. wide tower enclosing fan, motor, filters and fire suppression system can be mounted to the left, right or behind the hood. It can even be located up to 30 ft. away and ducted to the hood.

The backwall is constructed with a 3-in. air space, allowing zero clearance to combustible materials behind the unit. Vents at the bottom of the air wall also allow you to vent as much as 50% of filtered recirculated air under the cooking equipment.

The total coverage fire suppression system lets you mix and match equipment under the hood without having to change fire protection nozzles. You can put almost any combination of fryers, hot tops, griddles, ranges, broilers, ovens or steamers under the hood as long as it doesn’t exceed UL 197 or NFPA 96 specs. The 5-ft. hood, for example, can accommodate a 20-in. fryer and a 48-in. griddle. The 8-ft. hood can handle an 8-element, 72-in. range, four fryers, or two 36-in. broilers.

Depending on the configuration, the KVS moves anywhere from 1,100 to 2,250 cfm using heavy-duty, belt-drive, adjustable-pitch fans ranging in size from 2 hp to 5 hp. The units clean the effluent with a four-stage filtration system. Stainless baffles in the hood remove large grease particles. A pre-filter, back filter and HEPA filter in the tower remove most of the rest of the particles from the cooking effluent. After the air is filtered, a proprietary odor-neutralizing solution is atomized into the air stream before it’s recirculated into the cooking area.

Fully wired and plumbed for Ansul wet chemical fire suppression, the hoods are self-supported and come with the usual safety interlocks. You just plug equipment right into the unit. If the filters are dirty and need replacing, the system won’t provide power to the cooking equipment.

You can check out KVS specs at www.ventmaster.com or by calling Vent Master at 800/565-2981.

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