The document discusses ventilation systems for underground car parks, highlighting the importance of mitigating toxic gases released by vehicles. It compares natural and mechanical ventilation methods, detailing the advantages of jet fan systems over traditional ducted systems, including energy savings, flexibility, and cost efficiency. Additionally, it emphasizes the necessity of computational fluid dynamics for optimizing system design.

1. Mechanical Department
Faculty of Engineering
Alexandria University
Underground Car parking ventilation
Presented by / Mohamed Hashish
Mechanical Engineering Diploma
To prof Dr/ Mahmoud Basiouny

2. Underground Car parking ventilation
system
:Objectives
- Introduction
 Natural Ventilation
 Mechanical Extract
- Traditional Systems
- Jet fan or induction systems
- Technology and material Jetfan
- Operation of JetFan
- Examples of Fans for induction systems
- A control system
- Installation of JetFans
- Computational fluid dynamics (CFD)
- References

3. -Introduction
When cars enter, exit and drive through your enclosed parking garage, they release toxic
and non-toxic gases. If car engines were perfect, the vehicles would release carbon dioxide
(CO2), water (H20) and Nitrogen (N). Unfortunately, car engines are not perfect, and they
carbon),NOxoxides (various nitrogentypically release unburned fuel and fuel particles,
),O2) and water (H2(CO), carbon dioxide (COmonoxide
So Ventilation of car parks is important and also to clear smoke in the event of a fire
There are broadly two methods of complying with the Building Regulations regarding
ventilation and these are by natural or mechanical ventilation
Natural Ventilation
This is the preferred method of ventilating car parks and simply
requires openings to fresh air being provided to equal a percentage of
the floor area of the car park
Mechanical Extract
The rules for mechanical extract state that for control of fumes a system which is capable
of limiting the concentration of CO within the car park to below 30 parts per million
averaged over an eight hour period should be provided. For smoke clearance 10 air
changes per hour should be extracted.

4. Traditional Systems
(Ducted mechanical extract systems)
Traditional mechanical extract systems use sheet metal ductwork to transport the
fumes or smoke being extracted to the external atmosphere. The ducts must be
evenly distributed around the car park and also drop to low level to provide the low
level extract points.
The system should be capable of operating at temperatures of up to 300°C
for 60 minutes, and ductwork and fixings should be made from materials that have a
melting point above 800°C.

5. Ducted mechanical extract systems are permitted by regulations but are rarely used
nowadays
• The ductwork runs underneath the ceiling, reducing the already restricted height
normally available.
• Downstand beams require the ducting to be set down below them, thus diminishing
the height even further.
• Low level extract points are required, often needing protective
barriers to surround them, and these take up valuable floor space.
• High intial and running cost for maintenance

6. Jet fan, jet thrust, jet vent, impulse or
induction systems
All the above are different names for the same basic system
and have become increasingly popular as they can overcome many of the problems
associated with sheet metal ductwork.
Jet fans were developed for ventilating
tunnels a small jet of air at extremely
high velocity which causes surrounding
air to be entrained and in a confined
space like a tunnel or car park
can be used to move a large volume of
gas.
Impulse ventilation systems push the air
through the car park towards a single
extract point, rather than pulling it to
multiple extract points as a ducted
mechanical extract system would.

7. The number and location of fans are carefully chosen to match the system design
requirements and to ensure that there are no dead spots (where there is no airflow) for
fumes and smoke to stagnate and collect.
In addition to the space saving as well as dead spots are prevented jet fan systems have
other advantages over traditional ducted systems.
Energy saving
Jet fan systems are often combined with CO detection to initiate them for CO control and
these can ensure that fans are precisely controlled to dilute pollution without fans running
unnecessarily with large potential energy savings.
Low noise
Because the main extract fans are relatively smaller and for CO control run at lower speeds
than a traditional system the noise generated is considerably lower.
Low cost
Jet fan systems cost less than a comparable ducted system.

8. Jet fans
• the jet fans are positioned to ensure that fumes and smoke are transported quickly
and efficiently to the main extract points.
• jet fans can provide up to 50N of thrust, Suitable for most small to medium sized
car parks,induction fans can provide up to 100N of thrust, Suitable for medium to
large car parks
• Jetfans are flexible and can be adapted to suit changes in the use of space.
• the transferred volume of air being several times greater than the actual flow
volume of the fan.
Velocity profile of Jet Fan

9. Technology and material Jetfan
JETFans are available in many versions according to its sizes.
(Two fan sizes, 315mm and 400mm diameter, with overall depths of 335mm and
365mm)
The casing for all of these products is made of galvanised sheet steel and noise
suppressors integrated on both sides.
The impeller wheel usually is made of pressure die-cast Aluminium
The centrifugal impeller is made of sheet steel, welded and coated.

10. Operation of JetFan
The Jetfan can be used for partial smoke extraction ,ventilation or even in case of Fire.
In normal day-to-day operation, the Jetfans are controlled by the CO system – in
accordance with the concentration thresholdsetting. In this way, carbon monoxide-
contaminated air is extracted from the car park. This takes place with either just a few
Jetfans operating at a low speed, or with all system components operating at a higher
output level, depending on the concentration in the air.
The recommendation are that the system should provide 6 airchanges per hour (ACH) for
day-to-day ventilation on all levels and 10 ACH on the fire floor in the event of a fire.

11. Smoke extraction – the Jetfan smoke extraction system
In the event of smoke needing to be extracted, the Jetfans are immediately activated at
maximum speed by smoke detectors, regardless of the CO system setting, in order to
extract smoke from the area of the fire. The central ventilation shafts are switched
to full power at the same time.
A significant advantage of the Jetfan smoke extraction system lies in the fact that smoke can
be partially extracted from the immediate area of the fire. In other words, the Jetfans can
be used to control smoke levels as well. This avoids the costly process of dividing a car park
up into separate sections to reduce the spread of fire.

12. Examples of Fans for induction
systems

13. Jet thrust fan, jet fan, jet vent fan or
impulse fan:
An axial flow fan mounted within an
inlet and outlet cylindrical silencer.
jet fans canprovide up to 50N of thrust. Suitable for
most small to medium sized car parks.
Induction fan:
A centrifugal fan with an air inlet
positioned beneath the body of the fan
and discharging through a reduced size
opening, induction fans can provide up
to 100N of thrust.
Suitable for medium to large car parks,

14. TECHNICAL SPECIFICATION

16. A control system
 Description
designed to efficiently manage the
car park ventilation equipment. It
helps maintain good air quality
when the car park traffic is high
and conserve energy when it is low,
controlling operation of the fans
according to the conditions in the
space to save energy and will
usually incorporate CO sensors and
fans speed control.

17. Installation of JetFans
 Ceiling features
To make the system more effective, position JetVent Fans in-line with supporting
ceiling beams as illustrated in Figure 7(a). If this is not possible, the system becomes
less effective and more fans may be needed.
 Vertical clearance
Sufficient vertical clearance ensures maximum flexibility in system design. JetVent
Fans may be recessed between ceiling beams to minimise the height of the system.

18. • Obstructions
If there is no option and the JetVent Fans must blow across ceiling beams, have to be
positioned a sufficient distance away from the obstruction as illustrated A horizontal
distance eight times (8x) the height of the obstruction is generally sufficient. Nozzles
on the JetVent units are specially designed and angled downwards for this purpose.
• Clashes with other services
Place mechanical service components, such as sprinklers, signs and pipework out of
the JetVent’s discharge pattern area.

19. • fans placed in series
As shown at table below ,the maximum and recommended spacings between JetVent
Fans for different levels of fan thrust. These spacing distances are guidelines for fans
placed in series. When using these spacings.Analysis will determine whether this is
achieved in a particular car park design. In some ideal cases, designs using the
maximum distances have been effective.

20. Computational fluid dynamics (CFD)
CFD can provide detailed prediction of air movement,temperature and smoke density
throughout the car park, taking into account the often complex geometry of individual
buildings,This level of detail cannot be provided by any other means.
A Computational Fluid Dynamics (CFD) analysis is often required to prove and further
refine the design as Fans may need to be re-orientated, or in some cases, added or
removed.
The image shows the velocity vectors
produced by the CFD representation of a
Colt Cyclone 100 fan unit.

21. References
https://www.quora.com/What-type-of-air-ventilation-system-is-used-
for-basement-car-parks-in-malls
Fan solutions for underground and car parks
Colt ventilation systems for car parks, loading bays and service areas
http://www.althoffind.com/blog/why-you-need-to-test-your-
enclosed-parking-garage-ventilation-system-today
http://www.fantech.com.au/FanRange.aspx?AppID=P2&RangeID=2019
http://www.fantech.com.au/FanRange.aspx?AppID=P2&RangeID=2020