This is a filter for an Israeli civilian gas mask I bought on Amazon. It's only officially meant as a prop, but it's effectiveness as an actual filter is determined by how well you seal it, and whatever you stick inside as filter media...
The thread on GasMaskFilter_Top.stl is designed according to the NATO spec STANAG 4155. It's commonly referred to as "40mm NATO thread".
Update 2/11/2014: added NATO_STANAG_4155_40mm_Adapter_rev5.stl, which is just the 40mm thread model.
I originally designed this as a filter to get rid of acetone fumes when chemically smoothing 3D prints. I had success when placing activated charcoal pellets between two carbon filters, but of course this is not intended to replace proper respiratory protection. Try this at your own risk.
For basic assembly, you'll need the following:
- 1", #6-32 machine screws (x6)
6-32 machine nuts (x6)
I made the biohazard symbol green by starting with green filament and switching to black mid-print. However, I had some trouble removing the support material in between the biohazard symbol extrusion. You can see a lot of tool marks where I was struggling to get the material removed. In the future, I think it would probably be better to print the filter bottom and the biohazard symbol separately, and glue them afterwards.