Abstract:
The ventilation of underground car parks is important to avoid health problems with the inhalation of
combustion products released by car engines, in special CO (that is commonly used as the indicator of
indoor air quality). In last years, a new mechanical ventilation system appeared, based on the use of
axial ventilators (jet fans) suspended under the car park ceiling. In this paper the flow generated by jet
fans and their effects on the pollutants are studied. It is concluded that jet fans may have a pumping
effect entraining the surrounding contaminated air into the jet. In this way jet fans are able to restrict
the dispersion of the contaminants, provided that the exhaust flow rate from the car park is not lower
than the jet flow rate. Impulse ventilation may also provide fast dilution of the local pollution peaks,
but in this case the removal efficiency will be low. This paper also suggests criteria to define the
distance between jet fans.