Once we get to the place where we can agree that fluids and gases are “stored energy” and that those “stored energies” have to be bled/drained to achieve a Zero Energy State (ZES), we can then discuss the potential hazards these necessary actions can create. I have written a lot about using 1/4 turn ball valves as energy isolation devices and that once they are closed and locked, we now have a stored energy situation on the other side. We must provide a means to bleed/drain off the stored energy.
When the energy source is just plant air or water, we can bleed/drain the stored air/water pressure into the working space without creating serious hazards. However, when the gas or fluid we are dealing with is a hazardous material, bleeding or draining the gas/fluid into the occupied space, we could create a hazardous working environment.
For example: