How Air Conditioning Work

Tuesday, February 3, 2009



The following is a further description of some of the more common pollutants :-
i. Radon – radon is a colorless, odorless and radioactive gas. The main health risk of breathing air polluted with radon is lung cancer.
ii. Environmental tobacco smoke – it is the mixture of smoke that comes from the burning end of a cigarette, pipe or cigar and smoke exhaled by the smoker.
iii. Biological contaminants – viruses can be transmitted by people and animals. Water damaged materials and wet surfaces provide opportunities for molds, mildew and bacteria to grow.
iv. Pollutants from combustible products - wood, stoves and unvented kerosene and gas space heaters may be the source of pollutants from combustion products. The pollutants release carbon monoxide, nitrogen dioxide and particles.
v. Asbestos – it may be found in pipe and furnace insulation materials, shingles, textured paints and floor tiles when materials have been disturbed by cutting, sanding or removing activities.
vi. Lead – human may be exposed to lead through air, drinking water, food, contaminated soil, deteriorating paint and dust. Lead particles can result from lead dust from outside door sources and indoor activities using lead solder.
vii. Pesticides – it is used in and around a residence and may be used to control common insects, termites, rodents or fungi.

Air transferred from dining areas into kitchen keeps odors and heat out dining areas and cools the kitchen. Outdoor air intake and kitchen exhaust louvers should be located so that exhaust air is neither drawn back into the system, nor causes discomfort to passersby. Where odors may possibly be drawn back into dining areas, activated charcoal filters, air washers or ozonators may be used to remove odors. No kitchen, locker room, toilet or other odoriferous air should be re-circulated unless air purifiers are used.

Kitchens can often be air conditioned effectively, without excessive cost, if planned in the initial design phases. The relatively large number of people and food loads in dining and kitchen areas produce a high latent load. Additional cooling required to eliminate excess moisture increases refrigeration plant, cooling coils and air handling equipment size.

The kitchen has greatest concentration of noise, heat load, smoke and odors so that ventilation is the chief means of removing them and preventing these objectionable elements from entering dining areas. Kitchen air pressure should be kept negative relative to other areas, to ensure odor control.

The air quantity for proper ventilation is a function of kitchen equipment heat release and kitchen hood size. While the heat release factor is more important, canopy-type hoods do not operate at maximum efficiency unless entrance air face velocity is at least 75fpm. Face velocities of 75fpm to 100fpm should be used for design, with 60 fpm as an absolute minimum.

Slot-type exhaust hoods are more efficient than overhead hoods, but they are more costly and may diminish valuable work area unless properly applied. Slot hoods require 150cfm to 200cfm per linear foot for proper operation but many substantially reduce kitchen exhaust air requirements. Slot hoods may also reduce overall kitchen ventilation system cost by obviating an additional make up air system and related energy cost.


Ductwork should be designed for a velocity of 1800fpm to 2200fpm to minimize the settling of grease particles. All turns should be made with elbows that have a minimum centerline radius of 1.5 times duct dimension in the turning direction. When this is not possible, grease traps and cleanout panels may be provided in the ducts. Turning vanes should not be used.
The fan should be located at the discharge end of the duct run to minimize leaks, which could cause odor problems. Ductwork design must allow for sufficient expansion caused by high temperatures during a fire.

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