Or a California Style fume hood. They are pretty cheap considering what they do and you can find them at used equipment sales.
Building your own… when your life and the lives of the people who are near you and work with you. Brave soul.
How you get it to pass codes that way?
But really - if you need it to be giant - then the walk-in style is the way to go.
If you need it to be bigger than that - probably best to consider closing all your loop. If the equipment is that big, it doesn’t need to be open. And just put smaller exhaust units around the places you want to open things, with plenty of air changes per hour in the space around that.
PVC is used often for broad range of resistance to the fumes. Are you putting some acids and bases in there too? Or what?
So you want at least 6 air changes per hour - probably way more. I don’t know the size of your room - but you can calculate the total volume of the room and then times that by how many times you want the air to leave the space. And then you can buy an appropriately chemical resistance, potentially sparkless motor to fit your needs.
Don’t forget that you’ll need to put that much air back into the room/space as well. Or things like doors and stuff will be super hard to open.
If you are going with an enclosure with ventilation - you want the face velocity to be like 50fpm sometimes more (you’ll have a local code for this) and you can calculate that as well, so you know what size fan to get.
But really - you should be able to get one used or new for less than 10k. And it will be safer than just guessing.
Good luck and let us know what you decide to do!