CMC Hot Work Procedures 3

Question 1

Under NFPA 306, what classification is assigned to a space that is safe for workers but NOT safe for hot work?

Accepted Answer

Safe for Entry

Answer

'Safe for Entry' means atmospheric conditions allow worker entry but hot work is NOT authorized; a separate 'Safe for Hot Work' classification is required for welding or cutting.

Question 2

A welder reports that the flame on the torch repeatedly goes out during work inside a tank. What does this most likely indicate?

Accepted Answer

Oxygen concentration in the tank is dropping, possibly indicating displacement by inert gas

Answer

A repeatedly extinguishing flame can indicate falling oxygen levels caused by inert gas ingress, which is a serious life safety hazard requiring immediate evacuation.

Question 3

Which type of hot work presents the GREATEST risk of igniting vapors in adjacent spaces on a vessel?

Accepted Answer

Cutting through a bulkhead that separates two spaces

Answer

Cutting through a bulkhead creates a direct opening and introduces heat and sparks into the adjacent space, which may contain flammable vapors.

Question 4

Prior to issuing a hot work certificate, a Marine Chemist detects hydrogen sulfide at 5 ppm in a cargo tank. What is the appropriate action?

Accepted Answer

Deny hot work certification and require additional ventilation until H₂S is reduced

Answer

H₂S presence indicates incomplete gas-freeing and potential for higher concentrations; hot work should not be authorized until the space is fully gas-free and H₂S is at safe levels.

Question 5

A Marine Chemist is called to re-certify a tank after hot work was suspended for lunch. What is required before re-issuing the certificate?

Accepted Answer

A full atmospheric re-test of the work space and all adjacent spaces

Answer

After any work suspension, a full atmospheric re-test is required before hot work can resume, regardless of whether ventilation remained on.

(CMC) Certified Marine Chemist Practice Test

(CMC) Certified Marine Chemist Practice Test

CMC Hot Work Procedures 3