CMC CMC Ventilation Systems & Gas Freeing 2

Question 1

What NFPA 306 requirement governs the timing of gas testing relative to worker entry into a certified space?

Accepted Answer

Testing must be performed immediately before and continuously during entry

Answer

NFPA 306 requires initial testing immediately before entry and continuous or periodic monitoring throughout work to detect any change in atmospheric conditions.

Question 2

A Marine Chemist enters a tank and finds that LEL readings increase after 15 minutes of ventilation. What is the most likely cause?

Accepted Answer

Residual liquid or sludge is vaporizing as ventilation raises the temperature or disturbs the surface

Answer

Increased air movement and warming from ventilation accelerates vaporization of residual cargo liquid or sludge, temporarily raising LEL readings.

Question 3

Which ventilation configuration is described as "push-pull" in marine confined space practice?

Accepted Answer

One supply fan pushing fresh air in while a separate exhaust fan pulls contaminated air out

Answer

Push-pull ventilation uses a supply fan to introduce fresh air and a separate exhaust fan to remove contaminated air, maximizing air exchange efficiency.

Question 4

What is the minimum ventilation rate (in air changes) OSHA recommends to maintain safe conditions in a marine confined space during hot work?

Accepted Answer

At least sufficient to keep contaminants below PEL/action levels continuously

Answer

OSHA does not specify a fixed air change rate but requires ventilation sufficient to continuously maintain atmospheric contaminants below applicable PEL or action levels.

Question 5

Before conducting gas freeing operations on a tanker, what must be completed to prevent static electricity ignition?

Accepted Answer

Bond and ground the vessel to the terminal or yard

Answer

Bonding and grounding the vessel equalizes electrical potential between the ship and shore/yard, preventing static discharge that could ignite flammable vapors during gas freeing.

(CMC) Certified Marine Chemist Practice Test

(CMC) Certified Marine Chemist Practice Test

CMC CMC Ventilation Systems & Gas Freeing 2