CMC Atmospheric Hazard Testing 2

Question 1

When testing a marine cargo tank for flammable vapors, the Lower Explosive Limit (LEL) reading must be below what threshold before hot work is permitted?

Accepted Answer

5% LEL

Answer

1% LEL

Answer

10% LEL

Answer

25% LEL

Question 2

Which instrument operating principle is MOST susceptible to false readings in oxygen-deficient atmospheres?

Accepted Answer

Catalytic bead (pellistor) combustible gas sensor

Answer

Photoionization detector (PID)

Answer

Electrochemical oxygen sensor

Answer

Infrared hydrocarbon detector

Question 3

A marine chemist issues a 'Safe for Workers' certificate for a confined space. This designation requires oxygen content to be within what range?

Accepted Answer

19.5–23.5% O₂

Answer

16.0–23.5% O₂

Answer

18.0–22.0% O₂

Answer

20.0–21.0% O₂

Question 4

When sampling a large cargo hold for atmospheric hazards, the marine chemist should prioritize testing at which locations?

Accepted Answer

Multiple levels including low, mid, and high points plus remote corners

Answer

Only at the access hatch opening

Answer

Low points only, since vapors are heavier than air

Answer

Only the geometric center of the space

Question 5

Hydrogen sulfide (H₂S) IDLH (Immediately Dangerous to Life or Health) concentration is set at:

Accepted Answer

100 ppm

Answer

10 ppm

Answer

50 ppm

Answer

500 ppm

Question 6

A gas detector is bump-tested before use. What does a bump test verify?

Accepted Answer

That the instrument alarms respond to a known gas concentration

Answer

That the sensor is factory-calibrated to NIST standards

Answer

That the battery charge is above 80%

Answer

That the sampling pump flow rate is within specification

Question 7

Which condition is described as an 'oxygen-enriched atmosphere' under marine safety standards?

Accepted Answer

Oxygen concentration above 23.5%

Answer

Oxygen concentration above 20.9%

Answer

Oxygen concentration above 25.0%

Answer

Oxygen concentration above 22.0%