Understanding Carbon Monoxide Emissions

This question asks us to evaluate the correctness of three statements concerning carbon monoxide (CO) emissions.

Statement Analysis:

• Statement (1): Its mainly due to incomplete combustion of fuel.

  This statement is correct. Carbon monoxide (CO) is a toxic gas produced when fuels containing carbon (like gasoline, natural gas, wood, coal) burn without enough oxygen to convert all the carbon into carbon dioxide ($CO_2$). This process is called incomplete combustion. The general reaction is:

  $2C + O_2 \rightarrow 2CO$

  Complete combustion, in contrast, produces primarily $CO_2$ and water ($H_2O$). Incomplete combustion is common in many combustion processes, especially in engines and furnaces where oxygen supply might be limited.

• Statement (2): They are more evident in petrol engines.

  This statement is also correct. Petrol (gasoline) engines often run with an air-fuel mixture that is close to stoichiometric or sometimes slightly rich (more fuel than air). A rich mixture means there might not be sufficient oxygen for complete combustion, leading to higher CO production.

  Diesel engines, on the other hand, typically operate with a lean mixture (excess air), which generally promotes more complete combustion and results in lower CO emissions compared to petrol engines.

• Statement (3): Long term exposure can cause nausea.

  This statement is correct. Carbon monoxide is harmful because it reduces the oxygen-carrying capacity of the blood. CO binds to hemoglobin (Hb) much more strongly than oxygen does, forming carboxyhemoglobin (COHb). This impairs oxygen delivery to tissues and organs.

  While severe symptoms like headache, dizziness, vomiting, and confusion appear with acute (short-term) high-level exposure, prolonged exposure to even lower concentrations of CO can lead to chronic health problems. Nausea is a recognized symptom of CO poisoning and can occur even with sustained exposure, as the body struggles with reduced oxygen supply.

Conclusion on Statements

All three statements (1), (2), and (3) accurately describe aspects of carbon monoxide emissions, including its primary cause, its prevalence in different engine types, and a potential health effect of exposure.

Final Answer Derivation

Since statements (1), (2), and (3) are all correct, the option that includes all three is the correct choice.

• Statement (1) is correct.
• Statement (2) is correct.
• Statement (3) is correct.

Therefore, the correct option includes statements (1), (2), and (3).