What is tunnel ventilation system in Metro?

In emergency conditions, the tunnel ventilation system would be set to operate to control the movement of smoke and provide a smoke-free path for evacuation of the passengers and for the fire fighting purposes.

Are subway tunnels ventilated?

Metro systems consist of underground stations as well as tunnels, which connect these stations. Similar to rail tunnels, the ventilation system in the tubes is mainly used to transport smoke gases out of the tunnel in case of fire.

Why are tunnels ventilated?

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.

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.

Are subways bad for the environment?

People traveling on subway systems in major US cities are being exposed to unsafe amounts of air pollution, with commuters in New York and New Jersey subjected to the highest levels of pollution, research has found. The levels of these tiny specks of pollution, called PM2.

How do subways affect the environment?

The thermal environment in subways significantly affects human comfort and health, as well as related environmental factors such as IAQ, airflow, and sound transmission. The water vapor condensation, humidity radiation, and indoor air pollution lead to high temperature and humidity in a subway environment.

How do you ventilate a 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.

How drainage and ventilation of tunnel is done?

In this method of ventilation, vitiated air is sucked from the tunnel by using exhaust fans and fresh air is drawn into the tunnel through inlet shaft. This method rapidly removes dust and foul air from the working face of the tunnel but does not provide proper ventilation.

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.

What are the most polluted cities in the US?

15 Most Polluted Cities in the United States in 2021

• Bakersfield, California.
• Fresno-Madera-Hanford, California.
• Visalia, California,
• Los Angeles-Long Beach, California.
• Medford-Grants Pass, Oregon.
• Fairbanks, Arkansas.
• San Jose-San Francisco-Oakland, California.
• Phoenix-Mesa, Arizona.

How much CO2 does a subway produce?

A subway system like San Francisco’s Bay Area Rapid Transit, by comparison, will only produce about 125 grams of CO2 per passenger mile traveled, even when you factor in infrastructure.

Are trams greener than buses?

The study by researchers at Melbourne’s RMIT University, shows that – over the long term – trams produce the highest amount of greenhouse gases, followed by trains, cars and buses. They found that trams emit approximately 0.74 kg of carbon dioxide (CO2) per passenger kilometre.

How do you ventilate tunnels?

Such longitudinal ventilation systems can be provided using jetfans, Saccardo nozzles or using a push-pull arrangement with shafts. Depending on fire risk mitigation and the maintenance of adequate air quality, longitudinal ventilation systems can be installed in much longer tunnels.

Why is it essential to provide ventilation systems in tunnel during construction?

Hence it is essential to provide ventilation systems in in tunnel during construction. The main objectives of providing ventilation systems in tunnel are: To provide the working crew an environment of fresh air. To exhaust out fumes and gasses, that is injurious to health and explosive in nature.

What type of ventilation is used in underground railway stations?

Here mainly longitudinal ventilation is used- that uses ventilation plants at intermediate shafts or at the station adjacent. These may be either combined with exhaust from large caverns.

What is the direction of airflow in an air tunnel?

Here the direction of airflow is longitudinal in nature. At the beginning of the tunnel or the tunnel section starting, these moves the pollutant gasses and effluents, that is followed by the fresh air. Then at the end of the tunnel portal or at the tunnel section end, the polluted air is discharged.