I work as a paintball referee and a chronic problem that I have is my mask fogging up. I consider this the worst thing to happen on the paintball field, whether reffing or playing. As a ref, I can't keep track of players or accurately declare hits. As a player, even if my marker fails or I run out of paint, I can still be a diversion or a flag runner. Nevertheless, I'm pretty useless when I can't see. I've tried various anti-fog sprays, but they only last a game before giving up. The basic idea here is to put a fan in a paintball mask to continuously circulate air and remove humidity. Pretty simple, right?
Step 1: Materials and Tools
1 paintball mask
1 computer fan, 12v
2 slide switches, DPDT
1 resistor, 10 ohm
1 9v battery, preferably rechargeable
1 9v battery holder or connector
4 1" long bolts, must fit through holes in fan
4 matching nuts
4 small zip ties
Step 2: Getting Started
The first thing to do is to REMOVE THE LENS. Also make sure your fan works. You wouldn't want to put all this effort into it for nothing. Just hook it up to a 9v battery. Red goes to the smaller snap. Now make sure it's moving air out of the side with the support structure. Next you'll want to test fit the fan in your mask. The most convenient place for mine was right under my chin. If you put the mask on, you probably won't have enough room in there, so you'll have to trim down the sides.
Step 3: Fitting the Fan
The next step is to cut four corners off of the fan. These should be the corners facing away from where your face would be. Use the dremel with a cutting wheel attachment. You can clean it up with some sanding if you want but this side won't be visible after assembly.
Step 4: Protect Your Face!
Now if you don't want this thing to eat your face while you're using it, you'll probably want to put some sort of guard on it. I think there are commercially made ones available but zip ties work just as well. I drilled two holes on each side of the top half of the fan, where my chin might come in contact. Then I threaded two zip ties through the holes and secured them with another two.
Step 5: Mounting the Fan
After you mark the fan's mounting points on the mask, you can use a small dremel bit to cut them out. they should point in the direction of the mounting holes. If everything fits, just bolt it all together with the screw heads on the inside.
Step 6: Prepareing the Electronics
The switches perform two tasks. One determines the ON/OFF position while the other selects fan speed by incorporating the 10-ohm resistor.
Step 7: Soldering
Follow the schematic to assemble the switch group, being careful not to get the resistor too hot. It fits nicely between the prongs of the switch.
Step 8: Battery Clip Installation
Drill two holes side by side to hang the battery from. Insert the leads through the left hole and back in through the right hole. Secure with a knot.
Step 9: Switch Installation
Position the group to the right of where the battery sits(looking at the inside of the mask). Drill four small holes for screws and two slots for the switch arms. Secure with screws with wires leading towards the fan.
Step 10: Wiring
Solder the black battery lead to the center pole of the power switch. Connect the red battery lead to the red fan lead. Solder the remaining two wires together.
Step 11: Test and Finish
Now you can hook up a battery and see if it works. Use the lower setting to conserve battery power and the high setting for high humidity and heavy breathing conditions.I recommend coating all of the components in something like liquid electrical tape or truck bed liner(if you have it) for added protection. Oh yeah, and try not to get shot in the face.
Update: I tried it out for a day on the field and it kept the fog out for a solid three hours. I also used hot glue to cover all of the electrical components.