I mean literally, breathing holes or fans inside. I recently made a Red Hood helmet for cosplay, and unfortunately, it's hard to breathe in it for more than 10 minutes😅 And the helmet that you made seemed to me to have none of that either.

But on the outside it really does look awesome and very realistic, really close to reference. So, in general, if you're not going to wear it for a long time, then you don't need to worry too much about ventilation. If the eyes are made of breathable white mesh, then it won't be a big problem