Title: Reading Assignments
Course: WGF 106 DEVELOPMENT > Section: Content

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Sub-Title | Ventilation Basics: Capture & Exhaust (Fume Hoods) Versus Whole Building Ventilation (HVAC)
Content
An exhaust hood, extractor hood, or range hood is a device containing a mechanical fan that hangs above the stove or cooktop in the kitchen. It removes airborne grease, combustion products, fumes, smoke, odors, heat, and steam from the air by evacuation of the air and filtration.^[1] In commercial kitchens exhaust hoods are often used in combination with fire suppression devices so that fumes from a grease fire are properly vented and the fire is put out quickly. Commercial vent hoods may also be combined with a fresh air fan that draws in exterior air, circulating it with the cooking fumes, which are then drawn out by the hood.

In most exhaust hoods, a filtration system removes grease (the grease trap) and other particles. Although many vent hoods exhaust air to the outside, some recirculate the air to the kitchen. In a recirculating system, filters may remove odors in addition to the grease.

NFPA 96 Standard for Ventilation Control and Fire Protection of Commercial Cooking says that Mesh filters shall not be used. It requires that "Listed" grease filters shall be tested in accordance with UL 1046, Standard for Grease Filters for Exhaust Ducts.

The term HVAC refers to the three disciplines of Heating, Ventilating, and Air-Conditioning. A fourth discipline, Controls, pervades the entire HVAC field. Controls determine how HVAC systems operate to meet the design goals of comfort, safety, and cost-effective operation.

- Heating can be accomplished by heating the air within a space (e.g. supply air systems, perimeter fin-tube "radiators"), or by heating the occupants directly by radiation (e.g. floor/ceiling/wall radiation or radiant panels).
- Ventilating maintains an adequate mixture of gases in the air we breath (e.g. not too much CO2), controls odors, and removes contaminants from occupied spaces. "Clean" air helps keep occupants healthy and productive. Ventilation can be accomplished passively through natural ventilation, or actively through mechanical distribution systems powered by fans.
- Air-conditioning refers to the sensible and latent cooling of air. Sensible cooling involves the control of air temperature while latent cooling involves the control of air humidity. Room air is cooled by transferring heat between spaces, such as with a water loop heat pump system, or by rejecting it to the outside air via air-cooled or water-cooled equipment. Heat can also be rejected to the ground using geothermal exchange. Cool air is not comfortable if it is too humid. Air is dehumidified by condensing its moisture on a cold surface (such as a cooling coil), or by removing the moisture through absorption (desiccant dehumidification). In dry climates, humidification may be required for comfort instead of dehumidification. Evaporative humidification also cools the air. Radiant cooling systems and mixed mode cooling applications are being used where appropriate.
- Controls ensure occupant comfort, provide safe operation of the equipment, and in a modern HVAC control system enable judicious use of energy resources. HVAC systems are sized to meet heating and cooling loads that historically occur only 0.4% to 2.5% of the time. It is the function of the controls to ensure that the HVAC systems perform properly, reliably, and efficiently during all of the conditions that occur 97.5% to 99.6% of the time.
Links/Uploads | IDPH Guidelines for IAQ – IL Department of Public Health http://www.idph.state.il.us/envhealth/factsheets/indoorairqualityguide_fs.htm Capture & Exhaust (Fume Hood) – Wikipedia http://en.wikipedia.org/wiki/Exhaust_hood Building Envelop HVAC Integration – Whole Building Design Guide http://www.wbdg.org/resources/env_hvac_integration.php
Attributions
Image courtesy of Illinois Department of Public Health

Content by Wikipedia – The Free Internet Encyclopedia,

And additional content by:

Whole Building Design Guide – National Institute of Building Sciences