I spent a few minutes looking into this and usually it's a mix of outside air and recycle air. However, the key point seems to be that, with the exception of th

I spent a few minutes looking into this and usually it's a mix of outside air and recycle air. However, the key point seems to be that, with the exception of the Dreamliner, the air comes form engine bleed, rather than a dedicated compressor. So that's the issue. Maybe I should just bring a little scuba tank