[johnr2]

> ammonia is way too dangerous

The thought of working in the confines of a ship's engine room with such a hazardous fuel is horrifying. One reason for the widespread use of diesel oil is that it's relatively safe for human operatives.

[Grazester]

Engine rooms on these ships have large extractors and ventilation systems.

[DuskStar]

I'd look at that as "look how large of fans we need to make diesel safe", not "we have big fans and thus can use ammonia".

[Dylan16807]

Carbon monoxide is very dangerous. Removing that to replace it with the risks from ammonia could be a net improvement.