yeah, do not smell this.
technically this would be a fumehood chemical anyway, so you'd have to be quite dumb to go around huffing it.
personally id say its not the formaldehyde you should be worrying about (although, yeah, there will be formaldehyde vapor above the solution). it's the sulfuric acid. marquis reagent contains a damned lot of concentrated sulfuric acid, and... well, i happen to have somewhat accidentally inhaled some of its vapor.
acid and base vapors are unlike anything you've experienced in the normal world. the smell is overpowering and it burns your nose. its sulfurous, very burning, otherwise hard to describe.
and this was just from being too close to an uncovered beaker of it.
there are things that smell worse than sulfuric acid, or have more harmful vapors, but it's still up there.