Open-back Headphones

[MediocreNoob]

Quick question about open-back headphones, how "open" is open? I understand that with open-back headphones the sound leaks out the back and gives a more speaker like sound but due to newly developed medical issues the Razer Carcharias headset I'm using now just holds in the heat and makes my ears and head hotter. The main question is, if I were to buy an open-back headset and have a fan blow directly on my ear would I be able to feel it? Or is it just "open" to make it sound different?