And someone who used to do a ton of mask and costume work, glue continues to off-gas for a longer than it smells bad. Please, please, please... Don't make your costume at the last minute.
You need significantly less than you think you do.
I have seen too many that are beautiful sculptures in which the human inside is an inconvenience to the costume.
The ventilation problems with that particular costume character, were because the eyes weren't scrim and fogged. I wouldn't recommend this eye type for a long term wear.
maryrobinettekowal.com/category/puppe…
PPS if your convention wants me to talk about construction tricks for full body characters, I am happy to do that.
Also, the other problem with the poorly ventilated mask, is CO2 buildup.
Sorry. I apparently have strong feels about costumes and safety.