Bolt this to the top of a welding hood and have a gentle breeze to reduce lens fogging.
This is a work in progress. I've found it best to put batteries on a long lead so that their weight can be moved to a shirt pocket. This keeps the hood balanced with a light load.
-Drill 4 screw holes for 3 or 4mm bolts and one large 20mm hole in the middle of them to mount blower.
All additional parts are available from Amazon:
-Circuit board: Onyehn 2Pcs 1.8v 3v 5v 6v 7.2v 12v 2A 30W Low Voltage DC Motor Speed Controller PWM
-Blower: Comidox 5Pcs Black Brushless DC Cooling Blower Fan 5015S 5V 0.1-0.3A 50x15mm
-Battery holder: LAMPVPATH 3 Pcs 4 x 1.5V (6V) AA Battery Holder with 3 Pcs 9V I Type Snap Connector Plastic Housing