With reference to the role of long chimneys in factories, consider the following statements: 1. They are used to bring fresh air into the factory. 2. They take harmful smoke and gases away from our noses. 3. They release the smoke and gases high up in the atmosphere. Which of the statements given above is/are correct?

The correct option is (c). Explanation Industrial chimneys are vertical structures designed to vent hot flue gases or smoke from a boiler, stove, furnace, or fireplace to the outside atmosphere. Their height is a critical factor in the effective dispersion of pollutants. - Statement 1 is Incorrect: Chimneys are exhaust systems designed to expel waste gases produced during combustion or industrial processes. They do not function as intake mechanisms to bring fresh air into the factory. Fresh air is typically introduced through separate ventilation systems, windows, or intake vents. - Statement 2 is Correct: The primary purpose of a chimney is to transport pollutants away from the immediate vicinity of the source. By venting smoke and gases at a height, chimneys prevent these harmful substances from accumulating at ground level, thereby keeping them away from direct human inhalation in the immediate area. - Statement 3 is Correct: Long or tall chimneys release smoke and gases high into the atmosphere. Releasing pollutants at a higher elevation allows for better dispersion and dilution by upper-level winds, reducing the concentration of pollutants settling in the local surrounding area. Key Takeaway: Tall chimneys are used to disperse particulate matter and noxious gases high into the atmosphere to minimize local ground-level pollution; they are exhaust mechanisms, not intake systems.

NCERT Class 6 Environment & Ecology — Chapter 2: Air around us

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With reference to the role of long chimneys in factories, consider the following statements:

They are used to bring fresh air into the factory.
They take harmful smoke and gases away from our noses.
They release the smoke and gases high up in the atmosphere.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 and 2 only
B2 only
C2 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c).

Explanation

Industrial chimneys are vertical structures designed to vent hot flue gases or smoke from a boiler, stove, furnace, or fireplace to the outside atmosphere. Their height is a critical factor in the effective dispersion of pollutants.

Statement 1 is Incorrect: Chimneys are exhaust systems designed to expel waste gases produced during combustion or industrial processes. They do not function as intake mechanisms to bring fresh air into the factory. Fresh air is typically introduced through separate ventilation systems, windows, or intake vents.
Statement 2 is Correct: The primary purpose of a chimney is to transport pollutants away from the immediate vicinity of the source. By venting smoke and gases at a height, chimneys prevent these harmful substances from accumulating at ground level, thereby keeping them away from direct human inhalation in the immediate area.
Statement 3 is Correct: Long or tall chimneys release smoke and gases high into the atmosphere. Releasing pollutants at a higher elevation allows for better dispersion and dilution by upper-level winds, reducing the concentration of pollutants settling in the local surrounding area.

Key Takeaway: Tall chimneys are used to disperse particulate matter and noxious gases high into the atmosphere to minimize local ground-level pollution; they are exhaust mechanisms, not intake systems.

Your note

More from Chapter 2: Air around us

Consider the following statements regarding the atmosphere: 1. It is a thin layer of air that surrounds the earth. 2. It extends only up to 10 km above the surface of the earth. 3. The air becomes denser as we move higher in the atmosphere. Which of the statements given above is/are correct?

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With reference to the composition of air, consider the following statements: 1. Nitrogen and oxygen together make up approximately 99% of the air. 2. Carbon dioxide constitutes the majority of the remaining 1% of air. 3. The composition of air varies from place to place. Which of the statements given above is/are correct?

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Consider the following statements regarding water vapour in the air: 1. Air contains water vapour only during the rainy season. 2. When air comes in contact with a cool surface, water vapour condenses. 3. The presence of water vapour in air is essential for the water cycle in nature. Which of the statements given above is/are correct?

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With reference to the burning of fuel and its by-products, consider the following statements: 1. Burning can occur in the absence of oxygen if nitrogen is present. 2. Burning of fuel produces smoke which contains a few gases and fine dust particles. 3. Smoke produced by burning fuel is generally beneficial to respiratory health. Which of the statements given above is/are correct?

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Consider the following statements regarding the "dust particles" in the air: 1. Dust particles are always present in the air. 2. The presence of dust particles in air is constant irrespective of time and place. 3. Breathing through the mouth can allow harmful dust particles to enter the body. Which of the statements given above is/are correct?

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The correct option is (c).

Explanation

Statement 1 is Incorrect: Chimneys are exhaust systems designed to expel waste gases produced during combustion or industrial processes. They do not function as intake mechanisms to bring fresh air into the factory. Fresh air is typically introduced through separate ventilation systems, windows, or intake vents.
Statement 2 is Correct: The primary purpose of a chimney is to transport pollutants away from the immediate vicinity of the source. By venting smoke and gases at a height, chimneys prevent these harmful substances from accumulating at ground level, thereby keeping them away from direct human inhalation in the immediate area.
Statement 3 is Correct: Long or tall chimneys release smoke and gases high into the atmosphere. Releasing pollutants at a higher elevation allows for better dispersion and dilution by upper-level winds, reducing the concentration of pollutants settling in the local surrounding area.