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Extractor Hoods, Filter and Ducting Systems

Kitchen ventilation

Kitchen ventilation is the branch of Ventilation that specialises in how to deal with kitchen air, especially as this air is different from that of other types of environments as it typically contains grease, smoke and odours.

Restaurant kitchens often use large extractor hoods

An 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, smoke, odors, heat, and steam from the air by evacuation of the air and filtration.

The scope of equipment used in kitchen ventilation is typically described to comprise the extractor hood or canopy and the filtering system. The fan creating the airflow necessary for the ventilation might or might not be located in the kitchen.

Requirements

An adequate kitchen ventilation system should achieve the following objectives:

  • remove cooking fumes at the source, i.e. as near to the cooking equipment as possible
  • remove excess hot air and introduce incoming cool clean air so that a comfortable environment is achieved. Inadequate ventilation can cause stress, contributing to unsafe systems of work and high staff turnover.
  • ensure that the air movement in the kitchen does not cause discomfort
  • provide sufficient air for complete combustion at fired appliances, and prevent the risk of carbon monoxide accumulating
  • be easy to clean, avoiding the build-up of fat residues and blocked air inlets which lead to loss of efficiency and increase risk of fire
  • be quiet and vibration free

Kitchen ventilation design

The main factors that need to be taken into account when designing a kitchen ventilation system are:

  • workload of the kitchen
  • amount, type and power of cooking equipment used
  • layout and shape of the kitchen
  • number of staff working in the kitchen
  • the need for easy cleaning and maintenance
  • energy efficiency

Ventilation

The V in (HVAC) is the process of "changing" or replacing air in any space to provide high indoor air quality (i.e. to control temperature, replenish oxygen, or remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide). Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to keep interior building air circulating, and to prevent stagnation of the interior air.

Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.

 

 

"Mechanical" or "forced" ventilation

is used to control indoor air quality. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates much energy is required to remove excess moisture from ventilation air.

Kitchens and bathrooms typically have mechanical exhaust to control odors and sometimes humidity. Kitchens have additional problems to deal with such as smoke and grease. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. If ducting for the fans traverse unheated space (e.g., an attic), the ducting should be insulated as well to prevent condensation on the ducting. Direct drive fans are available for many applications, and can reduce maintenance needs.

 

Ceiling fans and table/floor fans circulate air within a room for the purpose of reducing the perceived temperature because of evaporation of perspiration on the skin of the occupants. Because hot air rises, ceiling fans may be used to keep a room warmer in the winter by circulating the warm stratified air from the ceiling to the floor. Ceiling fans do not provide ventilation as defined as the introduction of outside air.

 

 

Natural ventilation is the ventilation of a building with outside air without the use of a fan or other mechanical system. It can be achieved with openable windows or trickle vents when the spaces to ventilate are small and the architecture permits. In more complex systems warm air in the building can be allowed to rise and flow out upper openings to the outside (stack effect) thus forcing cool outside air to be drawn into the building naturally through openings in the lower areas. These systems use very little energy but care must be taken to ensure the occupants' comfort. In warm or humid months, in many climates, maintaining thermal comfort solely via natural ventilation may not be possible so conventional air conditioning systems are used as backups. Air-side economizers perform the same function as natural ventilation, but use mechanical systems' fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate

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