CMSP Mine Ventilation & Atmospheric Monitoring 2 — Questions and Answers
Question 1: What is the MSHA permissible exposure limit (PEL) for carbon monoxide in underground mine atmospheres?
- 25 ppm
- 50 ppm (Correct answer)
- 100 ppm
- 200 ppm
Correct answer: 50 ppm
MSHA sets a PEL of 50 ppm for carbon monoxide as an 8-hour time-weighted average in underground mines, consistent with established occupational health standards.
Question 2: In the Coward's Flammability Triangle, which three gases are used to describe explosive atmospheres?
- Oxygen, nitrogen, and carbon dioxide
- Methane (or fuel gas), oxygen, and nitrogen (Correct answer)
- Hydrogen sulfide, methane, and carbon monoxide
- Carbon monoxide, propane, and oxygen
Correct answer: Methane (or fuel gas), oxygen, and nitrogen
Coward's Triangle plots fuel gas (e.g., methane), oxygen, and nitrogen concentrations to identify the explosive zone, helping mine safety professionals determine whether a mine atmosphere is within the explosive range.
Question 3: What does a water-gauge manometer measure in a mine ventilation survey?
- Temperature difference between intake and return air
- The pressure differential (ventilation pressure) between two points in the mine (Correct answer)
- The percentage of methane in the mine atmosphere
- The total volume of air passing through an airway per minute
Correct answer: The pressure differential (ventilation pressure) between two points in the mine
A manometer measures the pressure difference between two locations in the mine, allowing engineers to calculate resistance and fan performance in the ventilation circuit.
Question 4: Auxiliary ventilation in underground mining is used to:
- Replace the main mine fan when it fails
- Ventilate dead-end headings and development faces where main airflow cannot reach (Correct answer)
- Provide emergency breathing air in rescue operations
- Reverse airflow direction during a mine fire
Correct answer: Ventilate dead-end headings and development faces where main airflow cannot reach
Auxiliary ventilation systems (using line brattice or duct-and-fan setups) extend ventilation into blind headings and development entries that are not on the main airflow circuit.
Question 5: Which type of ventilation system is characterized by two separate airway systems where intake and return air travel in opposite directions through parallel entries?
- Homotropal ventilation
- Antitropal ventilation (Correct answer)
- U-tube ventilation
- Forcing ventilation
Correct answer: Antitropal ventilation
Antitropal (or counterflow) ventilation has intake and return airways traveling in opposite directions and is considered safer for coal mines because it separates fresh and contaminated air in parallel entries.
Question 6: In a flame safety lamp, what indicates the presence of flammable gas (methane) in the mine atmosphere?
- The flame turns blue and goes out
- The flame elongates and develops a blue cap above it (Correct answer)
- The glass darkens and becomes opaque
- The flame turns red and increases in size
Correct answer: The flame elongates and develops a blue cap above it
When methane is present, it ignites and creates a characteristic blue halo or elongated blue cap above the main flame, with the height of the cap indicating the approximate concentration.
Question 7: What is the purpose of conducting a ventilation survey in an underground mine?
- To identify areas where blasting operations can occur
- To measure airflow quantities and pressures to evaluate ventilation system efficiency and plan improvements (Correct answer)
- To locate hidden ore deposits using air sampling
- To determine worker exposure to noise levels in mine entries
Correct answer: To measure airflow quantities and pressures to evaluate ventilation system efficiency and plan improvements
A ventilation survey measures air quantities, velocities, and pressures throughout the mine to assess whether the ventilation system meets regulatory requirements and to identify where improvements are needed.
CMSP Mine Ventilation & Atmospheric Monitoring 2
What is the MSHA permissible exposure limit (PEL) for carbon monoxide in underground mine atmospheres?