Two designs for Powered Air Purifying Respirators (Panfab PAPRs) with modular and interchangeable components were engineered and tested to NIOSH-equivalent standards. Specifically, the following top level components were developed-

• Custom made Blower Unit (known as Custom Blower Unit, repository titled “PanFab Powered Air Purifying Respirator- Custom Blower Unit”, NIH 3D Print Exchange Model ID: 3DPX-015674)
• Custom made Filter (known as Custom Filter, current repository)
• Blower Unit with modified commercially available housing (known as Commercial Blower Unit, repository titled “PanFab Powered Air Purifying Respirator- Commercial Blower Unit”, NIH 3D Print Exchange Model ID: 3DPX-015671)
• Filter Assembly with modified commercially available HEPA filter (known as Commercial Filter, repository titled “PanFab Powered Air Purifying Respirator- Commercial Filter”, NIH 3D Print Exchange Model ID: 3DPX-015673)

The devices were tested on human subjects including healthcare workers, under a protocol approved by the Partners Healthcare Institutional Review Board. PanFab PAPRs provide superior respiratory protection as compared to N95 masks and avoid the issues with fit common with those masks. These low cost PanFab PAPRs also performed favorably compared to commercially available PAPRs in terms of comfort and sense of security. The associated designs are available under a non-restrictive Creative Commons license. 
This repository provides CAD files of parts pertinent to the Custom Filter, that are to be 3D printed or injection molded.
For a detailed discussion of design and testing, please read the pre-print found here: https://www.medrxiv.org/content/10.1101/2021.03.25.21252076v1