PAPR v1

Update - version 2 is [here](https://www.thingiverse.com/thing:4290081).

This is a collection of fittings/housings to make a powered air-purifying respirator from a standard 3M respirator. The point is to overcome leakage from facial hair and (hopefully) to reduce fogging under a welding mask.

I revised my [prototype](https://www.thingiverse.com/thing:2839022) to use a [centrifugal fan](http://www.amazon.com/gp/product/B00B2ARV22) rather than an axial fan, and it seems to be just what I wanted now.

Hm, the fan link seems broken so: https://www.amazon.com/gp/product/B00B2ARV22/

It uses some anesthesia tubing that I had, so you'd have to adapt the design to whatever tubing you decide to use.

Edit: added a straight feeder pipe out of the blower and a diffuser I may try for use in a confined mask without the respirator. Happy to upload F3D files if anyone wants them.