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Multistory above and below ground car parks are becoming more common due to increased public reliance on cars as well as the congestion in towns and cities resulting from higher population densities. Motor vehicle engines running within an enclosed space will result in poor air quality and the confinement also increases the potential threat of smoke inhalation in the event of a fire. It is essential to ventilate covered car parks in order to limit users to the harmful effects of exposure to carbon monoxide (CO) and other toxic vehicle emissions.

Another important consideration when designing ventilation systems is smoke extraction. The major cause of death in the event of a fire is due to smoke inhalation. A smoke extract system is essential to enable occupants to escape before being overcome by smoke and to facilitate access for firefighters in order to extinguish the fire.

The most significant development to the car park industry in recent years has been the introduction of proven tunnel ventilation fan principles in the form of impulse fans.Impulse fans also known as jet fans are low profile ceiling mounted fans and provide air at a velocity to provide momentum to produce air movement towards an exhaust point.

Impulse fans are generally installed on the underside of the car park ceiling locating the fan inlets and outlets close to the ceiling.

Plan view of a traditional ducted system versus an impulse system:

This principle differs from the conventional ducted system in that whilst there is some supply air for fresh air makeup, impulse fans are located in strategic positions within the car park, usually in the centre of the driving lane, to push air towards the exhaust points. The supply and exhaust points may or may not utilise fans as normally expected with a conventional ducted system.

This innovative approach provides major benefits in terms of smoke control as well as reduced capital installation costs. Impulse fans eliminate the need for distribution ductwork with resultant lower extract system resistance, reduced power consumption by the fan/s and resultant savings in terms of system running costs.

Smoke extract requirements and regulations are on the increase in South Africa. AMS have responded to the requirement for ventilation and smoke extraction in car parks with the launch of their local centrifugal impulse fan unit.

Three of these impulse fan units with a thrust of 150 Newtons, were supplied by AMS for installation in an enclosed car park in Cape Town's V & A Waterfront.

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