RULE FOR WATERTIGHT AND GASTIGHT CONTROL MARKINGS

Observance of the rules for the control of watertight and gastight openings is the responsibility of ALL PERSONNEL and they must be continually aware of which watertight and gastight condition is in force and also of the requirements of each condition. Watch on the maintenance of the condition set is kept by NBCD patrols or by frequent rounds by the Watch on deck or Duty Watch according to the state of readiness, and the type and size of ship. The rules for control markings are:-

·         ‘X’ SHUT IN ALL WATERTIGHT CONDITIONS. To be opened only by permission. If required to be kept open, then a sentry must be posted or other arrangements made for the opening to be shut instantly on order, or a ‘MBLO’ disc must be used.

·         ‘Y ’SHUT IN CONDITION Y AND Z. Open in condition X-ray. When shut, may normally be opened for passage or use but must be immediately shut again. If required to be kept open in conditions Yankee or Zulu, the rules as for X-ray opening apply.

·         ‘Z’ SHUT IN CONDITION  Z. Open in conditions X-ray and Yankee. When shut, the rules as for Yankee openings apply.

·         ‘A’ SHUT IN CONDITION A. When condition Alfa is in force, openings so marked are not to be opened without specific permission from HQ1.

·         ‘M’ in condition Alfa only, openings so marked are under the control of the user department. User departments must ensure that the orders regarding their ’M’ openings are clear and fully understood by their personnel.

·         ‘R’ Fittings and equipment so marked must continue to run or remain open for recirculation.