CMC CMC Toxic Gas Detection & Monitoring 2

Question 1

What is the TWA (Time-Weighted Average) PEL for carbon monoxide established by OSHA?

Accepted Answer

50 ppm

Answer

OSHA's 8-hour TWA PEL for carbon monoxide is 50 ppm; exposure above this level requires respiratory protection.

Question 2

Which marine cargo residue is most likely to produce benzene vapor requiring PID monitoring?

Accepted Answer

Crude oil and petroleum distillates

Answer

Crude oil and petroleum distillate residues are primary sources of benzene vapor, a known carcinogen requiring PID or specific benzene tube monitoring.

Question 3

When calibrating a multi-gas detector for marine use, what gas mixture is typically used for LEL calibration?

Accepted Answer

50% LEL methane in air

Answer

Standard practice uses a certified calibration gas of 50% LEL methane in air (approximately 2.5% methane) to set the LEL sensor response.

Question 4

A Marine Chemist finds H2S readings of 3 ppm in a cargo tank. What should the certificate state?

Accepted Answer

Safe for workers with H2S monitoring in place

Answer

Low-level H2S (below 1 ppm ACGIH TLV) may permit entry with monitoring requirements noted on the Marine Chemist certificate.

Question 5

What type of detector is required when evaluating a tank that previously held leaded gasoline?

Accepted Answer

PID with an appropriate lamp plus lead-specific monitoring

Answer

Leaded gasoline residue presents both LEL and benzene/VOC hazards, requiring a PID in addition to standard combustible gas testing for complete hazard assessment.

(CMC) Certified Marine Chemist Practice Test

(CMC) Certified Marine Chemist Practice Test

CMC CMC Toxic Gas Detection & Monitoring 2