As I recall the first steampunk prop I ever made was the bad air transmutator respirator, which I still sell for $225 on Etsy. Ever since then, I've been wanting to design another respirator that I could sell for less. I make both respirators and gas masks, and the distinguishing feature in the nomenclature that I use is that respirators cover just the mouth and nose, whereas gas masks also cover the eyes.
I made a series of sketches to work out the design. I wanted to use mostly rivets in the construction, which is less labor-intensive than either machine- or handsewing.
Initially I wasn't going to provide any resin canisters as another cost savings measure.
Ultimately I decided to add two smaller identical canisters, as functionally it made little sense to have none.
Once I was happy with the pattern I tested it in green paper, and when that looked like it was working I cut it out of leather and riveted it all together. I need to add straps and make a few alterations, but I think it's a good beginning.