Environmental Engineering Test 2 Nddc Scholarship

While CO2 is naturally occurring, high concentrations are lethal. At 7–10%, humans experience dizziness and unconsciousness within minutes. When the concentration reaches 20%, it causes immediate convulsions and death due to the total displacement of oxygen and the rapid acidification of the blood (hypercapnia).

Methyl iso-cyanate is a very extremely toxic gas. During the Bhopal disaster, even brief exposure to low concentrations caused pulmonary edema and death. Its Threshold Limit Value (TLV) is less than 1 ppm, meaning even microscopic amounts in the air are considered unsafe for human exposure.

The environment inside a subway or a bus in heavy traffic is significantly louder than a normal office. It typically registers at about 95 decibels. This is the level where prolonged exposure (more than 45–60 minutes) can begin to cause hearing fatigue and eventual damage if experienced daily without protection.

Volatile organic compounds (VOCs) like gasoline and ether have low boiling points and high vapor pressures. In the confined space of a municipal sewer, these liquids can vaporize and mix with air to create a highly flammable and explosive atmosphere. A single spark from maintenance work or static electricity can trigger a massive blast.

Noise in fans is directly related to the tip speed of the blades. To maintain the same airflow while reducing noise, you can use a slower fan. To compensate for the slower speed, you must either increase the number of blades or increase the fan diameter to move the same volume of air. Therefore, both strategies are used in industrial noise control.

Soluble organic matter (like sugar, alcohol, or sewage) serves as food for aerobic bacteria. As these bacteria consume the organics, they use up the dissolved oxygen in the water through respiration. This leads to oxygen depletion, which can suffocate fish and other aquatic organisms, leading to a 'dead' water body.

Carbon monoxide (CO) and Carbon dioxide (CO2) are odorless. Nitrogen dioxide (NO2) has a faint sweetish smell but is mostly known for its color. Sulphur dioxide (SO2), however, has a very distinct, pungent, and irritating odor, often described as the smell of a freshly struck match. This makes it easily detectable by the human nose even at relatively low concentrations.

The term carcinogenic is derived from 'carcinoma' (a type of cancer) and 'genesis' (creation). Therefore, by definition, any chemical or substance classified as a carcinogen is one that is known to promote the formation or development of cancer in living tissue.

BOD is a critical parameter used to measure the organic pollution level in industrial effluents and municipal sewage. It represents the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material. While potable water should have a very low BOD, the term is most significantly applied to waste streams to determine their environmental impact before discharge.

Chlorine is the most widely used water disinfectant globally. It is highly effective at killing bacteria, viruses, and other pathogens by breaking the chemical bonds in their molecules. Benzene hexachloride is a pesticide, and ABS is a detergent, neither of which are suitable for making water safe to drink.