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Jet fans versus ducts

Jet fans might help ease the situation when smoke is trapped in a closed car park, claims the presentation

| | May 30, 2011 | 11:00 am
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Jet fans might help ease the situation when smoke is trapped in a closed car park, claims the presentation

Paul Mason, Business Development Manager, Solar & Palau, in May made a presentation in Dubai on the topic: ‘Ventilation of enclosed car parks with jet fans’.

Apart from raising awareness on hazards caused by smoke in closed car parks during a fire, Mason introduced fan products that he claimed would help mitigate the hazard. The presentation discussed the subject under the following rubrics:

  • Pollution /fume extraction
  • Emergency fire smoke extraction
  • Fire smoke clearance
  • Fire smoke control

Mason, delineating on the subject of safety in the event of fire, spoke on the importance of emergency smoke removal from occupied space for safe evacuation of occupants and for easier fire fighter access, either by natural ventilation or through powered ventilation. He stressed that protection of emergency escape routes was essential, and enumerated the following steps to be taken:

  • Create positive pressure to resist smoke entry to escape route
  • Use of pressure relief to atmosphere to balance door openings
  • Provide sufficient airflow through door openings and gaps to resist smoke flow
  • Provide positive smoke control in the protected escape routes

Mason explained that in a fire-smoke emergency, air has to be both supplied and extracted in a controlled, judicious and selective manner to deal with the situation. He pointed out that traditionally, ducted ventilation is used in many car parks, wherein, air is extracted through ducts. He said that this method came with a caveat: the air supply would be uncontrolled and an increase in fan pressure could conflict with other services, for example, lighting and pipework. Besides, ducts take up space, Mason said.

Elucidating the point, he said that a ducted system with extracts at high and low level would extract only hot smoke at a high level extract point. Thus, the amount of smoke extracted would be reduced. On the other hand, the jet fan system operated at a high level and induced hot smoke to move towards the extract point.

Highlighting the features of the jet fan system, Mason explained that the main extract fans provided controlled airflow, so that the required air rate was supplied to the parking space, and that the air was drawn in via ramps, louvres and shafts or supplied by fans.

Mason listed the advantages jet fan ventilation had over ducted ventilation:

  • No ducting in the parking area, reducing fan pressure, kW, SFP
  • More space for parking, improved visibility and appearance
  • May reduce height of parking space, saving building cost

On the other hand:

  • Ducting is prone to damage and obstructs other services
  • Needs cleaning and maintenance

Driving home the point with the help of illustrative images, graphs and tables, Mason claimed that the jet fan system not only helped reduce the smoke density and temperature during a fire by a conducive and acceptable air movement, but also assisted fire-fighters by providing ventilation to allow speedier clearance of smoke, once the fire had been extinguished.

Going into the finer points of how the system worked, the presenter explained that a CO detection system would be used to monitor CO levels within the car park. With pollution detection in place, the ventilation system would run on demand, he said.


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