JNTU B.Tech II MINE ENVIRONMENTAL ENGINEERING - I Previous Question Paper (July/August - 2021 - R16)

Methane (CH₄) is a colorless, odorless, and tasteless gas. It is non-toxic to the human body, meaning it does not have any direct chemical effect on physiological functions or blood chemistry. However, it acts as a simple asphyxiant. Because it is lighter than air (specific gravity approximately 0.55), it tends to accumulate in the roof cavities of mine workings. Its primary physiological danger arises not from its own properties, but from its ability to displace oxygen in the atmosphere, leading to hypoxia if concentrations become sufficiently high.

When a physiologically indifferent gas (such as methane or nitrogen) gradually displaces oxygen in a mine atmosphere, the physiological effects on the human body depend on the reduction of the oxygen percentage by volume. The progression of symptoms is as follows:

• 15% to 17% Oxygen: The first signs of oxygen deficiency appear, characterized by increased breathing rate and depth, and a slight increase in pulse rate.
• 10% to 14% Oxygen: Physical exertion becomes difficult. The individual experiences dizziness, headache, rapid fatigue, and impaired coordination. Judgment becomes clouded.
• 6% to 10% Oxygen: Nausea and vomiting occur. The individual may lose consciousness suddenly. Mental processes are severely impaired, and the person may be unable to perform self-rescue.
• Below 6% Oxygen: Breathing becomes gasping and irregular. Convulsions may occur, followed by cardiac failure and death within a few minutes due to severe cerebral hypoxia.

Because the intrusion is gradual, the body may not immediately trigger an alarm response, leading to a state of euphoria or confusion where the individual fails to recognize the danger until they are physically incapacitated.