2139. U.S. regulations require a responsible person to be present at all times when the hatches of spaces containing Class 1 explosive materials are open. When is the responsible person released from the duty of attendance?

The responsible person's attendance requirement ends only when the hatches containing Class 1 explosives are secured. This regulation is tied to the hatch status, not cargo operations, paperwork, or watch relief; the duty persists until the hatch is secured.