If you should decide to raise the bar for Certificates of Competency candidates, I would recommend that some research be carried out prior to composing your content. Typically, the following regulatory understanding would form a pre-requisite for any STCW III/1 CoC holder to carry his job covering air compressors, in a safe manner:

Starting Arrangements of Internal Combustion Engines from the IACS document (www.iacs.org.uk)

M61.1 Mechanical starting arrangements

M61.1.1 The arrangement for air starting is to be such that the necessary air for the first charge
can be produced on board without external aid.

M61.1.2 Where the main engine is arranged for starting by compressed air, two or more air
compressors are to be fitted. At least one of the compressors is to be driven independent of the
main propulsion unit and is to have the capacity not less than 50 % of the total required.

M61.1.3 The total capacity of air compressors is to be sufficient to supply within one hour the
quantity of air needed to satisfy M61.1.5 by charging the receivers from atmospheric pressure.
The capacity is to be approximately equally divided between the number of compressors fitted,
excluding an emergency compressor which may be installed to satisfy M61.1.1.

M61.1.4 Where the main engine is arranged for starting by compressed air, at least two
starting air receivers of about equal capacity are to be fitted which may be used independently.

M61.1.5 The total capacity of air receivers is to be sufficient to provide, without their being
replenished, not less than 12 consecutive starts alternating between Ahead and Astern of each
main engine of the reversible type, and not less than six starts of each main non-reversible type
engine connected to a controllable pitch propeller or other device enabling the start without
opposite torque. The number of starts refers to engine in cold and ready to start conditions.
Additional number of starts may be required when the engine is in the warm running condition.
When other consumers such as auxiliary engines starting systems, control systems, whistle,
etc., are to be connected to starting air receivers, their air consumption is also to be taken into
account.

Regardless of the above, for multi-engine installations the number of starts required
for each engine may be reduced upon the agreement with the Classification Society depending
upon the arrangement of the engines and the transmission of their output to the propellers.

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