Why are there fans under bridges?

The fans were installed to keep these gases from piling up in the tunnel. In addition to pushing out dangerous gases, jet propeller fans are also used to blow out smoke in the event of fire emergencies like the 1949 Holland Tunnel fire that happened under the Hudson River between New York and New Jersey.

What are Jet fans?

Jet fans – also known as impulse or induction fans – support the natural flow between the supply air and extract air zones. They provide motion in regions with low air speeds, thus guaranteeing the daily ventilation requirement for all areas.

What is tunnel ventilation?

Tunnel ventilation is a system where exhaust fans are located at one end of the house and two large openings are installed at the opposite end. Air is drawn through these openings, down the house, and out the fans, like a wind tunnel (see Figure 1). Tunnel ventilation is a type of exhaust system.

Why do tunnels vent?

Tunnels may require ventilation for a variety of reasons – for example to ensure an adequate air quality, to control the spread of smoke in case of fire, or to reduce temperatures to acceptable limits. The air velocity is usually measured using an anemometer and stopwatch.

What are impulse fans?

Jetstream is an impulse fan designed for the ventilation of car parks and underground service areas, so as both to reduce levels of polluted air and to assist with the extraction of smoke in the event of a fire. The fans use tunnel ventilation technology to eliminate the need for costly and bulky ductwork.

How do I choose a Jet fan?

Jet Fans are selected depending on their thrust value such as 20N, 30N, 50N, 80N and100N. They are selected also based on architectural design and their impact area to ensure there is no stagnant air in the car park( Image 2). no stagnant air in the car park. pollution in all floors of the car park.

Why is drainage necessary in tunnels?

Tunnel Drainage: During the construction of underground concrete lined structures like tunnels, it is necessary to prevent water from coming into contact with the completed tunnel lining that can cause both safety problems and increased maintenance costs.

Why is ventilation necessary in tunnels?

Tunnel ventilation is critical for a variety of reasons. Typically, ventilation ensures an adequate air quality, controls the spread of smoke in case of fire, and reduces air temperatures to acceptable limits. Cable tunnels require cooling, smoke control and a certain amount of air exchange.

Do you have to provide ventilation in tunnel?

Mechanical Ventilation System in Tunnels Mechanical ventilation system employs mechanical devices like electric fans, exhaust, and blowers, which serves the function of removing the exhaust gasses within the tunnel and help in blowing fresh air into the tunnel.

Which method is best for tunnel ventilation?

Combination of blowing in and exhaust system This method is generally considered as the most efficient system for ventilation of tunnels.

Where are Jet fans used?

Jet fans are used to distribute air within the car park and to ensure that “dead” areas do not occur. In most car parks, clearance is limited to approx. 2.4-2.5 m. It is therefore important to ensure that fans are installed where there is no risk of collision.

What is off spur tunnel?

i) Off-spur tunnels: These are short length tunnels to negotiate minor local obstacles, which cannot be avoided by permitted curves. ii) Saddle or base tunnels: These tunnels are constructed along the natural slopes till the slopes do not exceed the ruling gradient.