What scuba depth is safe without a stop in case of emergency?

The recreational Scuba dive depth limit is 130 feet. Keep in mind that skipping safety stops and avoiding decompression commitments is a function of depth AND time as well as each person's physiology individually. If you stay at almost any reasonable depth long enough you can push yourself into a decompression commitment. Normal divers on a single cylinder usually would run out of air before they build up enough of a nitrogen load but it is possible.