Certian bdsm "experts" like Wiseman claim breath play cant be done safely becuase of an increased chance for stroke or heart attack during play but his claims are not confirmed, tough some judo instructors that had frequent choke out submission holds preformed upon them over time did show signs of hypoxia induced brain damage.

Anytime you fiddle with O2 uptake and blood supply to the brain there is a certian amount of brain hypoxeia and cell damage does occur, and yes free divers and long distance swimmers can and do kill some brain cells when they ply their sports on occassion, but so do smokers and drinkers when they ply theirs.

Using your hands to stop carotid blood flow is ussually the safest so long as your not taking her to the point of unconsciousness, or repeatabely keeping her down near un-consciousness over and over in any given session, or over too many sessions over any given time frame. Like with anything else moderation is key.

A word on safe words:

Never ever use a safe word as a crutch or excuse, verbal, non-verbal or otherwise, dont think just becuase she doesnt safe word out for whatever reason that she wants or needs more of whatever it is.

The ultimate onis of responsibility for her saftey during any kind of bdsm play (including breath play) rests solely on the shoulders of you the dominant.

Besides "safe words or gestures" are hardely even close to reliable when your submissive is in the ultered state of estatic near-consciouness brought on by the oxygen deprived state of euphoria during breath play.

Ive done a lot of diferent kinds of breath play, everything from "queening" to "hanging" and as some of the others have pointed out, the safest form if of course using ones hand to apply gentle pressure to the carotid or to cup the mouth and nose.

But if you use any form of device, whatever you do, do not leave her unattended for any reason.

Remember: The number one cuase of bdsm related deaths is via self bondage asphyxiation.

Whatever you do, be prepared and know how to treat for shock, fainting, and or asphyxiation if they occur.