Interesting that in the first video you can see smoke coming from all four funnels. I have always read that the fourth funnel on the Olympic-class ships was a dummy funnel but clearly it must be venting smoke from either the engine room or perhaps the galley. So that should mean that all four funnels, at least on the Olympic at this stage in her career, were actually "working funnels".
>>By 1929, I think Olympic had been converted to run on oil or diesel instead of coal, and her 4 funnel might have been used to help vent fumes from the engines.<<
Not really. The change in the fuel only effected WHAT fired the boilers. How the effluent was exhausted was unaltered. There was no reason to change it.
The fuel the ship would have run on would have been the heavy marine oil of the day.
There were very few fumes from a steam recip engineroom, but the ventilation did go up the 4th funnel, along with the galley smoke. There's bound to be a chef burning something on a daily basis!By 1929, I think Olympic had been converted to run on oil or diesel instead of coal, and her 4 funnel might have been used to help vent fumes from the engines.