Invisible Helmets and Breathing

[Anthony]

The required holes for breathing are the same on an invisible helm as on a visible helm, its just that you don't need to deal with the hassle of making it possible to see while wearing the thing, which simplifies the design. I expect the lower part (below the nose) of an invisible helmet would be mostly indistinguishable from a conventional helmet, it just lets you replace the viewport area with a solid sheet of metal (this assumes that invisible helmets don't fog up like plastic would; antifogging would be a big challenge without rubber).