[QUOTE 2915243, member: 9609"]I'm guessing that blows clean air over the face ?
The reason I ask, I have got to that stage in life where I need reading glasses to see what I am doing - glasses are useless with dust masks as they just steam up. How would I get on with glasses with the thing in your picture ?[/quote]
The gizmo round his waste is a fan / rechargeable battery pack which draws air through a replaceable filter. The filtered air gets blown up the curly-whirly tube and gets blown down gently over your face. Because the helmet is at a slight positive pressure, no dusty air enters the helmet when you breath. Yes, you can easily use it wearing glasses but you have to keep the visor really clean to get good vision.
There are lots of different types.