User:Francis Farrell/sandbox

[[/Commercial Kitchen Ventilation]

Introduction
Humans have been cooking for many millennia using fire to provide the heat with natural ventilation. The chimney first appeared in the 12th century as an early form of controlling cooking emissions in kitchens large and small. In about ????? institutional kitchens (including restaurants, schools, hospitals, etc.) began using hoods with forced ventilation to remove the heat, smoke, water vapor and food emissions from cooking exhaust. (include a Schlieren image) Cooking food requires heat and produces water vapor, smoke, and emissions of food constituents. A ventilation system functions to remove heat, smoke, water and food emissions and any combustion products from kitchens and exhaust it outdoors. Figure 1 illustrates major ventilation components, namely the hood, followed by a fire-stop/filter, ducting, and a fan. To balance airflows, makeup air must be furnished in an amount approximately equal to the total exhaust flow. Food emissions, particularly greasy ones, collect as contaminant deposits on all surfaces in the ventilation system. They are fire and health hazards and a major concern for kitchen operators, building owners, safety, health and environmental officials, code authorities, and equipment manufacturers. Addressing the risks and costs of collecting and removing contaminants is an ongoing campaign and has been the major driver of both regulation and innovation in the field.

Ventilation Choices
The type of food and the cooking appliance are the key factors determining the required ventilation system. The amount of heat and quantity and types of food constituents emitted from cooking vary widely. Boiling vegetables on an electric range requires a very simple system while grilling fatty meat on a solid-fuel appliance requires a complex system. Typical building codes are the major determinant and will require a minimum level of kitchen ventilation for a new or substantially modified facility. The type of institution doing the cooking will play a role as well. A school kitchen will be allowed a relatively simple system while a chargrilling steak restaurant will require a more complex, and expensive, system. An increasing challenge is the trend of solid fuel cooking and the need for enhanced detection and suppression of fires caused by ignition of highly combustible creosote that’s added to grease in exhaust ducts with solid fuel cooking. Fortunately, there are many new equipment developments and installation techniques in response to challenges. It’s also important to emphasize that periodic preventive maintenance must be provided to enhance the safety of buildings that host commercial kitchens

System Components
Ventilation systems must be designed and installed to provide safety, comfort and economy. System components all play a role.

Listed & Unlisted Hood Types
Exhaust hoods are classified as either a Type I or Type II hood per International Mechananical Code (IMC) Section 507 (Ref). Type I hoods are designed for removing grease and smoke effluents, as vapors, liquid droplets, and solid particles produced by the cooking process and combustion of foods and fuels. Type I hoods must include grease filters or extractors classified to UL Standard 1046 – Grease Filters for Exhaust Ducts, and a fire suppression system listed to UL Standard 300 (Ref). Type II hoods are used for heat and condensate applications, without requirements for filters or fire suppression systems. Type I hoods can be listed by a testing agency to UL 710 – Standard for Safety Exhaust Hoods for Commercial Kitchen Cooking Equipment. Listed hoods are constructed in accordance with the terms of the manufacturer’s listing and are required to be installed in accordance with NFPA 96 or applicable local codes (Ref). The International and Uniform Mechanical codes allow Type I hoods to be exempt from code-specified exhaust rates if listed to UL 710 (Ref). Type II hoods are typically used for two different applications: condensate hood or as a heat and fume hood. Condensate hoods are used in applications with high-moisture exhausts, such as from dishwashing appliances. Hoods for these applications are designed to direct the condensate, which forms on the interior surfaces of the hood, toward a gutter located on the perimeter of the hood. The gutter allows for collection and drainage of the condensate instead of dripping down onto the cooking surface. Exhaust rates for Type II hoods are generally in the ranges of 100-150 CFM per foot of the hood length. Unfortunately, exhaust hoods for dishwashers are often undersized in many applications, allowing heat and moisture to escape from hoods, which contributes to discomfort from heat and humidity in kitchens. Based on experience and testing, large overhangs are recommended for hoods over conveyor dishwashers, such as 12 inches in front and 24” at inlet and discharge ends. (Ref – CAS booklet) Another use of Type II hoods is exhausting equipment producing only heat and water vapor, such as steamers. Typically, exhaust rates for these applications are in the range of 100-300 CFM per foot, depending on the application. Per the IMC and NFPA 96, the use of Type II hoods over ovens and other appliances is allowed; subject to verification that grease effluent discharge is less than 5mg/m3 per cubic meter when tested at 500 cfm, per UL 710B (Ref). The minimum exhaust flow rates required by the International Mechanical Code (IMC) for unlisted hoods. Backshelf and wall canopy hoods are shown below. (Ref)

TYPE OF HOOD	CFM PER FRONT FOOT OF HOOD (do as a table) LIGHT DUTY 	MEDIUM DUTY	HEAVY DUTY	EXTRA-HEAVY DUTY Unlisted, Wall-Mounted Canopy	200	300	400	550 Unlisted, Backshelf	250	300	400	Not allowed

Listed hoods are recommended to be used in all applications because of the lower exhaust rates per foot. Typical minimum exhaust rates for listed wall canopy and backshelf hoods are shown in the table below. NOTE: Specific manufacturer listed minimum exhaust rates could vary (Ref).

TYPE OF HOOD	CFM PER LINEAR FOOD OF HOOD  (do as a table) LIGHT DUTY 	MEDIUM DUTY	HEAVY DUTY	EXTRA-HEAVY DUTY Listed, Wall-Mounted Canopy	150 - 200	200 - 300	200 - 400	350+ Unlisted, Backshelf	100 - 200	200 - 300	300 - 400	Not Recommended

Hood Styles
There are many considerations when determining the appropriate hood model. It is important to review local code requirements before specifying a hood style. Also, location of the job site, kitchen layout (walls, doors, pass through and drive through windows, etc.), and building and heating, ventilation and air conditioning (HVAC) design, including exhaust air volume, are important factors to know in advance. Other considerations are cooking equipment sizes, types, locations under hoods, equipment use, and food products cooked. (Do as a table) •	 Wall Mounted Canopy - covers cooking equipment located against a wall •	 Backshelf, Proximity or Low Profile - covers counter height equipment •	 Single Island Canopy - covers cooking equipment in a single island configuration •	 Double Island Canopy - covers cooking equipment in a back to back configuration •	 Eyebrow - mounts on top fronts of appliances such as ovens and steamers •	 Recirculating - covers electric appliances without grease effluents, generally discharging heat and moisture into the kitchen space •	 Type II Hood - condensate or heat and moisture applications, discharged outdoors

In-hood Filters
Removing grease deposits from exhaust hoods, filters, hood plenums, exhaust ducts, and fans is well known requirement of commercial kitchen operation. Grease anywhere in the exhaust system is literally fuel waiting to burn. Significantly, with solid fuelcooking, typically aromatic species of wood, creosote deposits in exhaust ducts are added to the fire risk. With increasing attention of local jurisdictions, pollution and odor emissions are additional concerns. Type I hoods are required by mechanical codes to have grease filters, baffles, or extractors listed or classified to UL Standard 1046 –Grease Filters for Exhaust Ducts. Such filters are tested to ensure their capability to remove grease, draing it a proper collection device. Ffilters are also tested for compliance with a specified maximum projection of flames beyond the filters. The amount of grease removed varies based on the type of cooking (appliances and foods), filter efficiency related to particle sizes, and airflow through the filters. Other requipment might also be applied to reduce emissions. Grease Particle Capture Efficiency Testing grease filters to UL Standard 1046 does not measure grease filter extraction performance. ASTM F 2519 – Standard Test Method for Grease Particle Capture Efficiency of Commercial Kitchen Filters and Extractors, provides a realistic, reliable, and repeatable means of measuring the grease removal performance of kitchen hood filters. Kitchen exhausts includes grease vapor and small particles. Typically, higher temperature appliances, such as charbroilers and woks, generate smaller sized grease particles and more grease vapor than those produced by lower temperature appliances, such as ovens and fryers. The ASTM F 2519 Standard generates a challenge aerosol, using oleic acid to create emissions having similar particle size and distribution characteristics of real-world cooking, between 0.3 and 10 microns in diameter. An optical particle counter is used to measure the number and sizes of particles passing through the tested filter. The result is a capture efficiency percentage graph across a particle size range up to 10 microns. Manufacturers genenerally submit their filters for independent testing under ASTM F-2519 and publish particle removal efficiencies. The adjacent graph compares grease collection efficiencies of three different filter options. In the sample chart, the gray line in the graph above shows that between about 8 and 10 microns, the sample baffle filter captured approximately 20 to 30 percent and at 5 microns, efficiency was only 6 percent. In comparison, the 2-stage filter (dark green line between 8 and 10 microns, captured 100 percent. Because more efficient filters have a greater static pressure or resistance to flow, exhaust fan size might need to be increased.

Pollution Contol Unit
Concerns about indoor and outdoor air quality have led to increasingly stringent standards for commercial kitchen exhausts. In many cities, with increasing numbers of multi-use buildings, additional air treatment might be required. Various types of pollution control equipment are available, with technologies than include multi-stage filtration, electrostatic precipitation, and water mist or scrubbers. Multi-stage pollution control units employ a series of mechanical filters to remove grease and smoke from kitchen exhaust. Typical equipment might includes a high efficiency filter for the removal of smaller grease particles, followed by a HEPA filter for the removal of smoke, and optionally, odor removal with filter beds of activated charcoal and/or potassium permanganate, such as shown in the adjacent drawing. In North America, pollution control units are tested to UL Standard 710, ULC710 and ULCS-646, and because large quantites of grease would likely be present, units must include fire suppression systems listed to UL Standard 300. Regular mMaintenance of these systems is an important. An initial mechanical filter might be cleanable, while following stages would likely be disposable and must be replaced periodically, as needed. Cleaning and replacement intervals are dependent on the cooking appliances, cooking processes, and foods. The better the grease filters in hoods, the less often pollution control units must be serviced.

Fire Suppression Systems
Fire suppression systems, tested and listed to UL 300, are required by codes and standards to be installed in Type I exhaust hoods. Systems are pre-installed by manufacturers or installed after hood installation by qualified installers. (Ref: https://en.wikipedia.org/wiki/Fire_suppression_system) Conventional fire suppression systems detect fires under hoods by fusible links that, when heated to a set temperature, release a tentioned cable, which pierces the seal of a pressurized gas, to discharge wet chemical suppressant for about one minute. These systems are powered by a cocked spring, so that they operate without electricity. By their UL 300 listings, these systems require testing and maintenance every six months. The growing practice of cooking with wood, or wood-assist to natural gas appliances has increased the risk of fires in restaurant kitchens because burning wood produces creosote vapors that are flammable at relatively low temperatures, condense as they cool, and deposit in cooler, upper sections of ducts beyond fusible link detectors. In response to this risk, newer fire suppression systems have been developed that feature electronic detection and operation, with battery backup. Newer fire suppression systems also feature newer enhanced means of suppression, such as with unlimited building water after limited wet chemical suppression, or unlimited building water with limited surfactant added to reduce the surface tension of water. Some newer systems are also monitored by electronic means for suppression readiness. Listings of these systems typically require testing and maintenance every six months.

Duct Systems
As part of the exhaust system, grease ducts convey effluents from exhaust hoods and filters to the outdoors.. Effective ductwork must be liquid-tight, sized properly to convey the exhaust volume, and be clear of combustibles by code-required distances.. Ducts used in Type I hood applications must also contain products of combustion in fire situations to prevent fire spread (Ref IMC). Ducts used in commercial kitchen ventilation systems can be either round or rectangular. Rectangular duct is typically fabricated by sheet metal contractors and welded onsite. Round ductwork is factory built and listed to UL Standard 1978: Grease Ducts. Testing and listing cover modular grease duct assemblies, unwelded connections between adjoining duct parts, fittings, access doors, and other accessories. Ducts for Type I hoods must be installed in conformance with listings, and comply with NFPA 96 or other local mechanical and fire codes.

Duct Materials and Construction
Applicable codes and standards provide minimum specifications for the materials, thickness, and constructions of of duct systems. For example, joints, seams and penetrations of grease ducts must be made with a continuous external liquid-tight weld or braze on the external surface of the duct, with exceptions in applicable codes and standards (Ref IMC). Clearance to Combustibles Grease duct exhaust fires can generate very high temperatures, which without proper clearance, can ignite combustible materials near the duct. Accordingly, codes and standards specifiy required clearance to combustible constructions, such as 18 inches, or protection by external application of listed non-combustible materials, as described below

Listed Duct Systems
Factory-built grease duct systems are an alternative to code-prescribed duct systems that are welded or brazed on-site. Listed ductwork can be installed with reduced clearance to combustibles in accordance with the manufacturer’s listing and instructions. Available materials, such as duct wrap, can also be applied directly to the ductwork for clearance reduction to combustibles. These materials are tested to ASTM Standard E2336, “Standard Test Methods for Fire Resistive Grease Duct Enclosure Systems,” as written into recent IMC and NFPA Standard 96 editions. These materials are tested to five separate and distinct tests to verify the effectiveness of the enclosure. Available flexible wrap type enclosure systems typically meet all five criteria of ASTM E2336 if applied in a minimum of two insulation layers. It is important to find materials that have met all the requirements of ASTM E2336; and moreover, are thinner, lighter, flexible, and offer installation advantages. Duct enclosures are used when grease ducts penetrate fire-resistance-rated wall or floor-ceiling assemblies; the duct must be continuously enclosed from the point the duct penetrates the first fire barrier until the duct leaves the building (Ref). Both listed and welded ductwork are subject to the enclosure requirements laid forth by codes. Clearance must be maintained between the duct and the shaft when the duct is in the rated enclosure; NFPA Standard 96 and IMC require minimum of 6-inch clearance. The duct enclosure can also only contain one ductwork assembly. Some listed ductwork, which is tested to UL Standard 2221, is manufactured to be used without a shaft enclosure. Usually, this ductwork includes double wall construction and has fire-resistant insulation material between the two walls. This product must be installed in compliance with the terms of the manufacturer’s listing. Exhaust Airspeed. IMC and NFPA Standard 96 have set the minimum air speed for exhaust ductwork to be at 500 fpm. This is a change from the earlier requirement of 1500 fpm and allows for greater flexibility in design and especially, the use of variable-speed exhaust systems. Helping the change was ASHRAE sponsored research which revealed that velocities below 1500 fpm caused less grease deposit on horizontal duct runs (Ref). Recommendations for Design and Installation. When designing a duct system for an application, the most ideal installation would be a straight duct run from the hood upwards to the exhaust fan above. If thhis is not possible, the design should minimize system effects such changes of direction, offsets, elbows, and fittings close to each other, all of which can increase the static pressure the exhaust fan must overcome. To avoid increased system effects and added static pressure, the following recommendations are suggested: •	Run exhaust ductwork straight up to the inlet of the exhaust fan; or if needed:; •	First elbow should be least 18” above the hood; •	Allow for minimum of 4 feet between elbows; •	Use radius back elbows instead of mitered elbows; and •	Avoid placing an elbow directly before the exhaust fan inlet.

Exhaust Fans
A fan is required to pull the cooking emissions into the hood, move it through the ducts and exhaust it into the atmosphere. Fan physics are given in Affinity Laws. The most common types of fans are described below.

Centrifugal Upblast
are the most popular fans for light and medium duty applications because of their relative lower cost than other fan types. The outer shells of these fans are constructed of aluminum

Utility Set
fans are usually constructed of steel, mounted outdoors and used for high static pressure, high temperature, and high exhaust rate applications. Both curb mounted and side inlet utility set models are available. When selecting utility set fans, it is recommended to keep the discharge velocity at less than 1800 FPM.

Inline fans
are used in applications where an exterior installation or rooftop installation is not possible. Instead, these fans are located in the duct run inside of a building and are constructed of steel, Motors for this hood type must placed out of the exhaust stream. As with hoods, manuracturer’s sales engineers can suggest fan types and sizes for particular applications.

Fan Drives
Belt drive fans can handle higher static pressure and exhaust rates than direct drive fans and are generally a better choice when using with a variable speed exhaust systems, but belt drive fans usually have more maintenance associated with belts, pulleys and, bearings. Direct drive fans have less friction while operating, with speed controlled by varible frequency drives and associated controls. The reduction is friction increases operating efficiency and lowers operating costs by eliminating periodic belt and bearing replacement.

Fan-location Terminations
Rooftop terminations are preferred because the discharge heated exhaust can contine rising, to some extent if the motor fails, exhaust can be directed away from buildings, and exhaust fans are more accessible for duct and fan cleaning. Fan Actions in Fires Exhaust systems must be designed and installed to prevent a fire starting in the grease exhaust system from damaging the building and to prevent the spread of the fire through the grease exhaust system. In fire conditions, exhaust fans are generally required by codes to remain on, to help carry the fire suppressant liquid through the duct and remove combustion products from the building. Supply fan are required to turn off during fires to avoid feeding more oxygen to the fire. Fan Laws & Energy Savings (reference: https://fishnick.com/ventilation/oalc/oac.ph & https://en.wikipedia.org/wiki/Affinity_laws)

Electrical Control Packages
Electrical control panels are available in single phase, three phase and mixed voltage configurations. They typically include starters to operate makeup and exhaust air fans, and switches to control those starters in conjunction with the hood fire suppresion system. Spare terminals controlled by the fire system are also included. Electrical control panels are typically factory pre-wired to shut down supply fans in a fire condition, and to keep on or turn on exhaust fans in a fire condition. Automatic Fan Operation International Mechanical Code (IMC) section 507.2.1.1, requires that Type I hood systems be designed and installed to automatically activate exhaust fans whenever cooking operations occur. Several methods are indicated in the code to achieve this operation, such as heat sensors in the hood. When the sensor temperature is higher than the kitchen temperature by a set number of degrees, exhaust fans are turned on. Forms of variable-speed exhaust systems are also used to meet this code requirement. Recent Advances	(from when 1st code or standard was written – including: safety, efficiency and comfort)

Makeup Air Equipment and Outlet Location
These input air into the ventilated space to balance the quantity of air exhausted through the hood. There are several types and flow paths by which the replacement air can be directed.

Front Face Discharge
Supply makeup air outward through the upper front of the hood, through louvers or perforated metal. Since the air is directed outward into the space, much of air can become heating and cooling load on the HVAC system. In addition, if speed and direction of the air is not considered, face discharge can reduce hood performance

Air Curtain
Introduce makeup air in a downward direction at the front edge of the hood. Typically the discharge velocity of the air supplied is too high and effectively creates a barrier for capture and containment. The higher discharge velocity can also cause the effluent to spill out into the kitchen. Makeup air being supplied by this method is recommended to 20% of the exhaust flow, according to the CKV Design Guide 2, Improving Commercial Kitchen Ventilation System Performance.

Backwall Supply
Can be an effective strategy for applications that cannot use a perforated perimeter because of space constraints. This application can be used to bring in a maximum of about sixty percent of the exhaust air and the discharge area should be at least 12 inches below the cooking surface of the appliances. If these guidelines are not followed, the makeup air could interfere with the cooking equipment, including pilot lights, as well as becoming cooling or heating load.

Perforated Perimeter Makeup
(might this be considered too much a CAS term?) Perforated perimeter makeup air is released from about 18” above the front lip of the hood, on available outer hood surfaces, downward toward the capture area of the hood. Lab testing and field experience indicate that this method is a relatively efficient means of providing makeup air near the hood.. Makeup air that’s about 70-80 percent of the exhaust rate can be provided by this method. Airspeed and temperature of the air delivered by this means is an important consideration in adjusting performance of this method. With one manufacturer’s product, discharge airspeeds should be in the range of 140-160 fpm downward from the perforated plenum when used with wall mounted canopy hoods. The makeup air supply is typically heated to 55 °F and the first stage of cooling of the makeup air is initiated when the outdoor temperature is 85°F or higher. The perforated supply devices can also be placed on ends of wall canopy hoods or on all sides of island hoods. A variation of perimeter supply is available with dual plenums. With this concept, partially tempered dedicated make-up air is directed to the inner plenum as usual. Fully tempered outdoor or recirculating aur from one or more heating and cooling units is provided to the outer plenum, instead of through customary 4-way diffusers in front of the hood, which have been found to interfere with hood performance (Ref). Both single and double perimeter supplies evenly distribute air along the length of the hood, discharging downward through adjustable perforated stainless steel diffuser plates. Because lights in the ceiling above the hood might be obscured by this equipment, at least one manufacturer offers an LED light option on the underside of the perimeter makeup plenums.

Tempered Makeup Air
The IMC requires makeup air to be conditioned to within 10°F the kitchen space, except where the replacement air does not decrease the comfort of the kitchen. This requirement can be met by having all replacement air come directly from HVAC units, with makeup the air tempered to a range of 68 to 75 degrees, for example;. however, since much of this air is immediately exhausted, many restaurants are furnished with dedicated makeup air that is only partially tempered, such as heating the makeup air to about to 55 degrees F and cooling it when the incoming air is above 85 degrees F. Tempering methods of makeup air can include indirect and direct fired gas heat, heat pumps, evaporative coolers, and most predominantly, direct expansion cooling. Direct-fired natural gas heating is generally the most efficient and economical means of dedicated make-up air heating. Makeup air units with heating can typically be modulated to maintain a set temperature, instead of on/off heating operation. Direct-fired heating equipment burns gas directly in the fresh air stream, providing the lowest cost per BTU of heating when compared to indirect-fired and heating. Below are some of the benefits to the using direct fired units: •Direct fired heating is a more thermally efficient process than indirect fired units. Typically direct fired heaters are over 90% efficient, while indirect heaters are about 70% efficient. •Direct fired heating is environmentally clean and equipment is listed to the ANSI Z83.4a and CSA 3.7a safety standards, which set maximum concentrations of carbon monoxide and nitrogen dioxide (CO and NO2) potentially generated by these heaters. •Direct fired heaters can operate on either natural or propane gas and achieve high temperature rises.

Codes, Standards, Regulations
(insert UL, ASTM, NSF, NFPA, IMC descriptions and appropriate detail

Hoods Sizing for Proper Capture & Heat Load
When determining the appropriate hood length, the following must be considered: hood length = overall equipment length, plus spaces between sides of appliances, plus side overhangs. Side overhang is defined as the distance from outside edge of the cooking equipment, to the internal end of the hood canopy. Experience and testing (Ref) have shown that increased side and front overhang can improve system performance, in terms of improved capture, containment, and removal of heat, grease and water vapors, and other cooking effluents (Ref.). Recommended side and front overhang are shown in the table below (Ref): For upright, open flame, and solid fuel broilers, with heavy cooking loads, 18” minimum front and side overhangs are recommend, if possible. The additional overhang will ensure that the rapidly rising and expanding effluents are captured and contained by the hood. From experience and testing, 18” minimum overhang is recommended on all sides of single island exhaust hoods. (Ref) Most hoods from north American manufacturers are available in one piece up to 16 feet long. If the total length of the cooking line is greater than 16 feet, multiple the hoods installed. Two exhaust risers are recommended on hoods greater than 12 feet, especially those with heavy cooking loads(Ref – CAS booklet.

Recommended Overhang
Though exhaust hoods have customarily been tested and listed to UL Standard 710, with estimated cooking temperatures, there is movement toward classifying by the light, medium, heavy, and extra heavy duty ratingss defined by appliance type in the International Mechanical and similar model codes. General practice is to group appliances by their duty rating. If multiple duties are under a single hood, the exhaust rate will be based on the highest duty rating for the entire hood length (Ref). The adjacent chart will help determine the cooking temperature of some common types of equipment (Ref).

Ducting Sizing
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Exhaust Fan Selection
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Makeup Air Unit Selection and Outlet Location
(move some content from above here) A goal of dedicated makeup air is to introduce close to the hood, so that partial tempering is sufficient and without negatively affecting hood performance. Many designs have been tried in the industry throughout the years to bring in makeup air including short-circuit hoods, front face discharge, front air curtain backwall makeup and most recently perforated perimeter supply. Limitations of some designs described below.

Flow Visualization
Schlieren flow visualization is a thermal imaging technology that allows observation of heat and effluents generated by the cooking process, otherwise ‘invisible’ to the naked eye, and usually in a laboratory testing process. Smoke and sometimes steam may be visible. Other effluents including convective heat, water vapor, grease vapor, and combustion by-products are all invisible. A schlieren system aid can aid visualization of effluents by illuminating the refraction of light with changes in air temperature and density. The result is a well-defined, real-time image illustrating the heat and effluent generated and associated flow patterns. Many of the concepts described below have been verified by laboratory use of schlieren systems. The accompanying schlieren images show different exhaust rates for a hood directly above a range top. On the image on the top, the thermal plume is escaping the hood with 165 CFM per linear foot of hood. The same hood, with an exhaust rate of 220 CFM per linear foot, shows that the hood completely capturing and containing the buoyant thermal plume.

Enhanced Fire Safety
(detectors, suppressants, controls)

Automated Hood Cleaning
(CORE-like self cleaning)

Dedicated Outdoor Air System (DOAS)
units are increasingly being used in areas with high humidity conditions, compared to temperatures. For example, the U.S. areas of Atlanta, Georgia, and Miami, Florida, on an annual basis, experience a latent (humidity) load that averages 6.7 times greater then the annual sensible (temperature) load (Ref Harriman et al or ASHRAE handbook). Recent breakthroughs in sensors, controls, and modulating equipment are contribiting to the efficiency of these products. DOAS units are often paired with standard rooftop units (RTUs), whereby the RTU is focused on controling temperature and the DOAS controls humidity. Balance Point The balance point temperature of a space or area with controlled by a thermostat, is the temperature below which heading is initiated, and above which cooling is initiated, though in practice, there is typically a temperature range of several degrees (deadband), in which the thermostat does not call for either heat or cooling. Commercial kitchens generally have relatively low balance points, typically between 50 and 60°F. It’s lower than the usual comfort temperature settings because of heat gains from cooking appliances, dishwashers, lighting, solar heating, and human activity. If the heating and cooling equipment in a commercial kitchen is not electronically coordinated or interlocked, heating and cooling can occur simultaneously, which can effect both comfort and energy costs. This issue is frequently seen during spring and fall seasons, when dining area RTUs might be heating and and kitchen RTUs might be cooling. Controls should be configured to eliminate this wasteful practice.

Demand Control Ventilation
Another means of meeting IMC section 507.2.1.1 code requirements, and saving energy, is the use of demand control ventilation systems, which control exhaust and supply airflow quantities while still completely capturing and containing effluents produced by cooking processes. The demand ventilation controls are activated through sensors, including temperature, optical, and/or infrared technologies. Instead of the exhaust system running at 100 percent all hours of kitchen operation, the exhaust rate is modulated in relation to the cooking load, often with a preset reduction for periods where there is little or no cooking. If the demand control system is also linked to the makeup air fan(s), there are added savings for space heating and cooling costs, as well as fan operating costs. The modulation of the fans between low and high speeds is typically controled by variable frequency drives and sensors that indicate the intensity of cooking operations. The purple line in the adjacent chart shows an example variation of fan energy controlled by a demand control ventilation system over a 12 hour period.

Operations
(demand venting rate, effluent management esp. grease, fire safety, cleaning)

Best Practices
(seminar contents very useful here) The concept of sustainability is quite profound and is the driver for a design for a fully integrated system. Commercial kitchen use more energy per area than many other building spaces.Owners and operators of modern commercial kitchens can expect to have efficient operations for sustainability, including cooking, space heating and cooling, and fire protection. Described in this article are several design principles that will increase efficiency and safety: •	Aerodynamic hoods, tested and listed to UL Standard 710, are the centerpiece of the kitchen ventilation system. Lower CFM rates can be achieved with listed hoods, compared to unlisted hoods that must meet code specified airflows. •	Determine the appropriate exhaust rate by grouping equipment by duty cycle, use hood end panels to increase hood efficiency, ensure correct placement of equipment particularly charbroilers and using correct overhang for both the side and fronts of hoods. •	Use advanced technology grease filters to remove more grease at the hood and use a pollution control unit if necessary for final grease, smoke and odor control if needed. •	Use direct drive fans where applicable, for energy efficientcy and lower operating costs •	Include a variable speed and makeup air, with. exhaust and supply airflow based on the cooking load, to avoid operating at full capacity during operating hours. •	Utilize of dedicated, partially tempered makeup that is disharged close hoods to avoid complelely coolking and heating air that will be immediately exhausted. energy and operating costs. •	Employ direct fired gas heating for dedicated make air, as posible. In areas of especially high humidity, pair standard rooftop heating and cooling usits with dedicated ourdoor air systems (DOAS) •	For enhanced fire safely, install listed ductwork and an electronically detecting and operated fire suppression system, especially with solidfuel cooking, and multi-story and multi-tenant buildings.