Not sure any policies I have would help being an Aussie - our laws are quite different but remembering from a lecture I gave some years back the precautions are:-
1) ALWAYS "mix" the cylinder (just move it around) before using as the gas can separate (Entonox is 50/50 nitrous and O2)
2) Must have a "self-regulator" on the gas delivery system
3) The patient and ONLY the patient is to hold the mask on thier own face. The theory of Entonox is that they have to press hard to get a good enough seal to be able to trigger a gas flow. When they have enough they lose consciousness and thier hand falls away from thier face and bingo! no more gas flow until they wake again.
4) Be careful to explain that Entonox may not actually take the pain away - it just might "divorce" them from the feeling of pain. They know on a level that the procedure is painful but they don't care and it does not worry them. From personal experience (dentist) I felt I was 2 miles down the road saying "Ooooh! Looky! I have pain! Good thing it is over there and I am over here!" :chuckle:
5) Don't use if there is a pneumothorax (can expand the pneumothorax)
6) keep locked away between use as it has been known to be abused by staff (like anything it can be addictive)
If you have further questions I do suggest asking in the CRNA forum - they would put my answer here to shame