The existing ventilation arrangements are entirely passive. At one end of the shelter is the access shaft and immediately adjacent to this is an air shaft, a second air shaft is at the other end.
This works OK but does not filter the air.

Lighting is battery powered, with candles in reserve.
Any ground water that enters is removed by a small hand pump.
No plumbing is provided, just a chemical closet.

This virtual tour gives a good idea of the design,
video tour of a bunker