Lay plastic bag flat on table. Bag must be well sealed, wide enough to loosely fit PAPR and long enough to reach shoulders. Sealed end of bag is top. Polyethylene "kick bucket" liners are nearly perfect size and strength..

Most bags are not transparent enough, but we can easily add a clear window. Any optically clear plastic sheet will work. For instance, a laser printer transparency sheet yields four usable windows.

Place window at desired location. Allow sufficient space between sealed "top" of bag and window. About 20 cm works, but adjust to position window in front of eyes.

Tape around periphery of window with clear plastic shipping tape. Overlap 1 cm of the window taking care to create a good seal.

Turn bag inside out and lay it flat. Carefully cut away the plastic overlaying your window. Try to cut nearly to edges of the window.

Apply tape to overlap the window again to create a window that is taped securely to the plastic bag on both inside and outside. Once taped, turn bag right side out.