Hello,
I also found this method on multiple autopsy reports and I wish to ctb using this. I am not an expert either but I can share what I found. The reaction is just a decomposition of formic acid, sulfuric acid serves as a catalyst (which is a really good thing because you don't need a lot of the latter, and the sulfuric acid has an unbearable smell). The reaction is the following:
HCOOH+H2S(cat) -> H2O + CO + H2S(cat)
So the reaction produces only water and carbon monoxide. I didn't test it but what should happen is, once you pour the formic acid into a bucket, you add a small amount of sulfuric acid and the liquid will start to boil, producing the CO.
The thing I'm unsure of the the quantity of formic acid needed to be lethal (in my case it will be in my car). The article says they found a 1-liter bottle of acid, and when the corpse was found, the reaction was still going (it happened also in a car). So I guess 1 or 2 liter of formic acid would be enough depending on the concentration.
I am not sure I am allowed to share the articles here, but you can find them or equivalents if you search "suicide formic acid" in google scholar.
I hope it could help, please message me if I was not clear on certain points or if you want to know more
