Cars have become a natural part of daily life. Despite the existence of extensive public transportation systems, most people today own a car. As a result, parking facilities—especially in large cities—are in high demand. Traditional open-air parking lots take up a great deal of space, while people often prefer parks and green areas in their cities.
In other cases, such as unfavorable weather conditions or the desire to protect parked vehicles from damage, enclosed parking structures are necessary. Consequently, more parking facilities are being built. Car exhaust contains several hazardous gases—most notably carbon monoxide (CO) and benzene—which must be safely removed from enclosed parking areas for safety reasons.
Theory of parking lot air exhaust system
Ventilation is the movement of air. To move air, a mass must be moved. At 20°C, the density of air is approximately 1.2 kg/m3. Therefore, ventilation of 10 m3 involves the movement of a mass of 12 kg.
The well-known method of conveying air through a duct is by using a fan that sucks or pushes air through the duct. It is also well known that air moves vertically in response to thermal differentials (the so-called chimney or stack effect). The jet fan ventilation method exploits the fact that a moving object changes its speed when subjected to a “pressure force”. In physics, this phenomenon is known as thrust.
When it comes to ventilation systems, there are two types of parking lots: open and closed. Even parking lots that are above ground can be a closed parking lot if there is not enough natural ventilation.
Parking lots that have open areas on one side connected to open space and these areas provide half of the required area for open parking lots according to the third topic of the National Building Regulations are considered semi-open parking lots and do not require the installation of fresh air ducts and vents. These types of parking lots must be equipped with a proper ventilation system.
In enclosed parking garages, mechanical ventilation is essential to minimize the concentration of hazardous gases such as carbon monoxide. Jet fans allow for the design of these ventilation systems without the need for bulky ductwork. Small jet fans are strategically placed throughout the parking area and can effectively ventilate large zones by inducing airflow.
These ventilation systems, which combine jet fans with low-pressure axial flow fans, are ideal for efficiently supplying fresh air and extracting polluted air from any parking facility. If axial fans are used—especially those directly exposed to the airstream—they must be certified for fire resistance, holding an F300 or F400 fire rating, depending on the specific safety requirements.
In conventional ventilation systems, all air is moved through fans and ductwork. This applies to both the supply of fresh air and the exhaust of used air. To prevent pressure loss, air velocity is kept as low as possible. However, this requires relatively large ducts, which in turn demand significant space.
Jet fans operate on the principle of impulse. Air is discharged at relatively high speed from a small outlet (the fan’s nozzle). When this air stream collides with the air in front of the fan, it pushes it forward while also entraining the surrounding air through the induction effect. This allows jet fans to move large volumes of air effectively, making them a space-efficient solution for ventilating enclosed parking areas.
The surrounding air will therefore move in the direction of the airflow. As a result of this induction or bubble, the amount of air moving will always be significantly greater than the amount of air passing through the fan itself.
This driving force is called the thrust or thrust force of jet fans and is expressed in Newtons [N]. Thrust is the product of mass flow rate and velocity change. Thrust is the unit of measurement for jet fans, unlike conventional fans whose output is measured in terms of volume flow [m³/s] and pressure [Pa].
The effect of jet fans on the surrounding air is only local. The effective working area of jet fans depends on the type and performance of the ventilation system.
Jet fans are strategically placed to ensure air movement and mixing throughout the parking lot. Combining this principle of draft ventilation with mechanical exhaust and fresh air supply (natural and/or mechanical) results in an optimal ventilation system for indoor parking lots.
In car parking facilities, jet fans can be used to replace ducts for extracting CO gas and ultimately liquefied (explosive) gas.
