Modern Marvels.
Use to love watching this show on the History Channel when I subscribed to cable TV. I was a History Channel addict. Now that I cut the cord and stream things, I ran into it again. It has it's own free streaming channel. 24-7 of Modern Marvels (although it loops through the same episodes every day but a new loop the next day).
How It's Made (I like that series too) also has it's own fee streaming channel. I should look to see if they have the Dirty Jobs series on a channel. That was another one of my favs.
Found it, Dirty Jobs is on Hulu.