Gotta finish off a project for an open-sided shelter over an engine service/inspection pit. Era is, oh, mid-60s.
What kind of roof ventilators would one expect to find on such a structure? Is anything produced as a detail part that might do (rather than something that needs to be fabricated)?
Since it’s open-sided, it wouldn’t have to be much; probably a cupola with louvered slats, like they used to use on barns and enginehouses in the old days. I was lucky: I wanted a couple of them but didn’t want to build ‘em myself because even using ESM styrene strips it would be a lot of fiddlin’. I hunted for months and finally found them, made with a 3D printer by a company called “Rusty Stump.” They were wonderful and he sold them in pairs, with or without flagpoles, in O scale (thank goodness, since that’s my scale), HO–and maybe even N. I bought a pair without flagpoles and they were worth the price, which was in the 'teens–20 bucks or so with the shipping. Unfortunately, like a lot of other “Basement Operators,” he wanted to retire and closed up shop. (When I was in HO, I planned to build some fancy cupola vents for a roundhouse, using ESM clapboard siding, inspired by a kit my brother assmbled in the '50s. Milled wood siding would work just as well, if that’s your medium.) I hope some of the HO guys out there will be able to help you. Good luck!
If the structure is open-sided, it might have a cupola, but it might not need even that.
For the small roundhouse on the upper level of my layout, I added smoke hoods in the roof framework, with exhaust stacks on the roof. It’s implied that each hood has a blower fan, but I didn’t bother modelling them, nor much other interior detail, either…
In all the steel mills in which I worked, locomotives ran in and out of the buildings constantly, and with the heavy trains, were almost always working hard.
Even if they had been steam locomotives, I doubt that many would have noticed much difference in the air quality.
We generally preferred to work on cloudy days, as the dirt and steel dust were harder to see - on sunny days, the air literally glinted with the floating particles.
I used Evergreen clapboard siding to build the ice house at Lowbanks, and also used it for the rooftop ventilators, as Deano mentioned…
I wouls start by looking at prototype engine facilities. When was it built? Was it up graded? What RR’s owned it? All play a roll in how those vents look and are set up. After doing the google bing thing, go into the hobby and see what is there. Dont forget regular roof vents as they might fit the “close enough” bill. Newer upgraded vents are just square duct. So kitbash and scratch might be simple as well. All depending on what the vent looks like.