The grilles at Parliament are a tad bizarre and, likely, the one on O'Connor that deals with the Heritage Place exit looks like it could be an add-on. The large grille in front of the Queen entrance to WEP, however/moreover, is exactly in the location where the glass elevator pavilion marked Parliament appears in the Citizen photo you uploaded. At Rideau there are only two grilles, pretty much equal in size, and one on each side of the street. I haven't examined the fan situation at Lyon but I have at Rideau and it appears the fans are mounted in the vent shafts. If you stand on the western end of the westbound platform I believe you can see the exhaust mechanisms in the shaft at the west end of the eastern platform. There would appear to be no such mechanisms installed in what I think to be the abandoned elevator shaft in front of WEP that now serves as a sort of passive chimney vent for the station below
The double grill at O'Connor and Queen, next to the the Heritage Place entrance is above the existing stairs. It looks very sloppy IMO.
Lyon seems to be the only station with straight forward ventilation shafts; one on each end of the station cavern, both the same size. I always imagined large fans at each end to suck smoke out of the station should there be a fire. Not really sure how that would work with the mess of various sized, randomly placed grills at Parliament and Rideau.
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