CMSP Mine Ventilation & Atmospheric Monitoring 1 — Questions and Answers
Question 1: According to MSHA regulations (30 CFR 75.323), at what methane concentration must all miners be withdrawn from an underground coal mine working section?
- 1.0%
- 1.5%
- 2.0% (Correct answer)
- 2.5%
Correct answer: 2.0%
At 2.0% methane, all miners must be withdrawn from the affected area; at 1.0% production stops, and at 1.5% all but those correcting the hazard must withdraw.
Question 2: What is 'blackdamp' as encountered in underground mining?
- A mixture of carbon monoxide and hydrogen
- A mixture of carbon dioxide and nitrogen that displaces oxygen (Correct answer)
- Pure methane gas that accumulates near the roof
- Sulfur dioxide released from blasting operations
Correct answer: A mixture of carbon dioxide and nitrogen that displaces oxygen
Blackdamp is a mixture primarily of CO2 and N2 that displaces oxygen and can cause asphyxiation; it is heavier than air and tends to accumulate in low areas.
Question 3: Which instrument is most commonly used to measure air velocity in underground mine airways?
- Barometer
- Manometer
- Vane anemometer (Correct answer)
- Psychrometer
Correct answer: Vane anemometer
A vane anemometer measures airflow velocity by using rotating vanes; it is the standard tool for ventilation surveys in mine airways.
Question 4: What is the minimum required oxygen percentage in the atmosphere of an underground metal/nonmetal mine according to MSHA (30 CFR 57.5005)?
- 16%
- 18%
- 19.5% (Correct answer)
- 21%
Correct answer: 19.5%
MSHA requires a minimum of 19.5% oxygen in underground mine atmospheres; below this level, the atmosphere is considered oxygen-deficient.
Question 5: What is the primary function of a main mine fan installed on the surface?
- Controlling methane ignition sources
- Circulating air throughout the entire mine to dilute and remove contaminants (Correct answer)
- Supplying compressed air to pneumatic tools
- Generating electricity for underground lighting
Correct answer: Circulating air throughout the entire mine to dilute and remove contaminants
The main mine fan creates the pressure differential that drives fresh air through the entire mine ventilation circuit, diluting and removing methane, dust, and other hazardous contaminants.
Question 6: In mine ventilation terminology, what is 'afterdamp'?
- Moisture-laden air entering from surface during rain
- The toxic gas mixture (including CO and CO2) remaining after a mine explosion or fire (Correct answer)
- Methane released after a coal pillar is extracted
- Cool air that enters through downcast shafts
Correct answer: The toxic gas mixture (including CO and CO2) remaining after a mine explosion or fire
Afterdamp is the toxic mixture of gases—including carbon monoxide, carbon dioxide, and nitrogen—that remains in a mine after an explosion or fire, and is a leading cause of post-explosion fatalities.
Question 7: A ventilation 'regulator' in an underground mine is used to:
- Increase total airflow produced by the main fan
- Reduce airflow in a specific airway to control distribution across the mine (Correct answer)
- Detect and alarm on hazardous gas concentrations
- Seal off abandoned sections permanently
Correct answer: Reduce airflow in a specific airway to control distribution across the mine
A regulator (typically a door or restricted opening) creates additional resistance in an airway to reduce airflow and redirect it to where it is needed, balancing the ventilation circuit.
CMSP Mine Ventilation & Atmospheric Monitoring 1
According to MSHA regulations (30 CFR 75.323), at what methane concentration must all miners be withdrawn from an underground coal mine working section?