CMC Chemical Hazard & Risk Management 2

Question 1

A confined space entry permit lists benzene as a contaminant at 4 ppm. The OSHA PEL-TWA for benzene is 1 ppm. What is the correct action before authorizing entry?

Accepted Answer

Ventilate the space and verify benzene drops below 1 ppm, then re-test

Answer

Benzene must be reduced below the OSHA PEL of 1 ppm through ventilation and confirmed by re-testing before entry is authorized.

Question 2

Which document provides the hierarchy of health hazard data sources a Marine Chemist should consult when evaluating an unknown shipboard cargo?

Accepted Answer

The cargo's Safety Data Sheet (SDS) Section 2 and Section 11

Answer

SDS Sections 2 (hazard identification) and 11 (toxicological information) are the primary sources for health hazard data on specific chemicals.

Question 3

During hot work in a tank that previously held crude oil, the atmosphere reads 0% LEL. A Marine Chemist must consider which additional hazard before issuing a Safe Work certificate?

Accepted Answer

Residual liquid pooled under gratings that could vaporize when heated

Answer

Residual liquid hydrocarbons trapped under gratings or in low spots can vaporize rapidly when hot work raises temperatures, creating an explosive atmosphere even when initial readings show 0% LEL.

Question 4

A cargo tank that carried methyl alcohol (methanol) shows 0 ppm on a combustible gas indicator (CGI) but the Marine Chemist still withholds the certificate. What is the most likely reason?

Accepted Answer

Methanol is not detectable by most catalytic bead CGIs below its flash point

Answer

Many catalytic bead combustible gas indicators are poorly sensitive to methanol; a zero reading may be a false negative, so a photoionization or colorimetric method should verify the atmosphere.

Question 5

The Threshold Limit Value-Short Term Exposure Limit (TLV-STEL) for hydrogen sulfide is 5 ppm. This means workers may be exposed to that concentration for a maximum of:

Accepted Answer

15 minutes, no more than 4 times per shift with 60-minute intervals between exposures

Answer

ACGIH STELs permit exposure at the listed concentration for up to 15 minutes, repeated no more than four times per shift, with at least 60 minutes between each short-term exposure period.

(CMC) Certified Marine Chemist Practice Test

(CMC) Certified Marine Chemist Practice Test

CMC Chemical Hazard & Risk Management 2