Boba helmets have a lot more airflow underneath than say Stormtrooper helmets. I've been trooping my Boba for almost 14 years and haven't put a CPU fan in there yet. With other helmets, yes, you need it. Like Jc27 said.....stay hydrated before your event, and on breaks drink more water, and then when done trooping, drink even more. You just have to know going in you're going to get hot and sweaty regardless. That's just a normal part of costuming. LOL