Question

Study the following statements and select the correct option.

Statement I : Air purifiers with high efficiency filters can be used at homes to remove particulate matters.
Statement II : Particulate matter from industrial emission can be removed using scrubbers.

• A. Statement I is correct and statement II is incorrect
• B. Statement I is incorrect and statement II is correct
• C. Both statements I and II are incorrect
• D. Both statements I and II are correct

Answer 1

The correct option is D Both statements I and II are correct

Any undesirable change in the physical, chemical or biological characteristics of air is called air pollution. Air pollutants are agents like gaseous compounds (SO₂, NO₂) or particulate matter (dust, soot) which pollute air.

Particulate pollutants can vary in their size. Particles larger than 10 micrometres in diameter tend to settle down within a day of their release, but smaller particles remain suspended for a longer time.

According to the Central Pollution Control Board (CPCB) particulate matter, having a size of 2.5 micrometres or less is extremely harmful for human health. These particles can easily pass through the respiratory tracts and can get lodged in the lungs causing irritation and breathing difficulties.

In order to remove PM 2.5, air purifiers with high efficiency filters can be used at homes. These will filter out very small particulate matter leaving behind clean air. Hence statement I is correct.

Figure : Air purifier

Scrubbers are air pollution control devices that use liquid to remove particulate matter or gases like sulphur dioxide which are present in exhausts from thermal power plants, industries, etc. Hence statement II is correct.

Scrubber consists of a tower-like structure with nozzles to spray lime or water. Dirty air containing particulate matter is passed into the tower. As the flue gases in the tower rise up, it is made to pass through a spray of water or lime. Sulphur dioxide present in flue gases (exhaust gas) reacts with water or lime solution to form calcium sulphite.Thus sulphur dioxide is collected as calcium sulphite and removed from the scrubbing tower. Clean air from particulate matter leaves the tower from top and is let out to the atmosphere through smokestacks (a chimney or funnel for discharging smoke).

Figure : Scrubber