The individual division officers are responsible for maintaining the list in good physical condition. The commanding officer, assisted by the DCA, is responsible for filling in the column marked Division Responsibility. The divisions concerned are responsible for securing fittings that are classified as XRAY or YOKE. The ship’s repair parties are responsible for securing ZEBRA fittings. MATERIAL  CONDITION OF READINESS The term material condition of readiness refers to the degree of access and system closure in effect at any given time. The securing of access fittings or systems limits the extent of damage that could occur to a ship. To prevent interference with normal operations, the ship does not maintain maximum closure at all times. For damage control purposes, naval ships have three material conditions of readiness. Each condition represents a different degree of tightness and protection. The three material conditions of readiness are called XRAY, YOKE, and ZEBRA. These titles have no connection with the phonetic alphabet. Furthermore, the titles are used in all spoken and written communications that concern material conditions. Condition XRAY provides the least amount of protection. It is set when the ship is in no danger of attack. Examples are when the ship is at anchor in a well-protected harbor or when secured at a home base during regular working hours. Condition  YOKE  provides  more  protection than condition XRAY. It is set and maintained at sea during peacetime and in port during wartime. It is also maintained in port during peacetime outside of regular working hours. Condition ZEBRA is set before a ship leaves or enters port during wartime. It is also set immediately, without further orders, when the ship is manning general quarters stations. Also, condition ZEBRA is set to isolate and control fires and flooding when the ship is not at general quarters. All watertight, airtight, firetight, and fume- tight access fittings belong to a certain classifica- tion of fittings. Although the fittings usually have a basic classification, a select group of closures within each of the three material conditions of readiness are modified. The purpose of the modified closures is to allow access to a space that is secured because of the material condition that is set. Once a material condition is set, no fitting within the condition is to be opened without prior authorization. Closures that are not modified require permission of the commanding officer to be opened. Permission to open a closure is obtained  through  the  damage  control  central (DCC) watch or the officer of the deck (OOD) when the ship is not manning the general quarters stations. Repair party officers control the opening and closing of all fittings in their assigned areas when the ship is at general quarters. Any change in the status of a fitting must be reported to DCC so that the ship’s DC closure log maybe updated. You may open a modified closure without any special  authorization.   However, you are not authorized to leave the closure open unattended. Through careful attention to these procedures, a ship’s watertight integrity can be maintained at a safe level. The following discussion will help you learn about each classification, how the classification is marked, what group of fittings have the classification, and when you may or may not open a fitting with that classification. XRAY fittings are marked with a black X. These  closures  are  secured  during  conditions XRAY, YOKE, and ZEBRA. You must not open fittings with this classification without proper authorization. You will find this classification on the following access closures: Doors  and  hatches  to  storerooms  and stowage spaces, including cargo ammuni- tion spaces Hatches that are provided with a scuttle and lead to magazines and handling rooms Bolted-plate manhole covers Escape scuttles not covered elsewhere Doors and hatches located only on the weather deck and below that are used to strike down stores and ammunition Access  to  an  aircraft  fueling  station compartment Access  to  escape  trunks  in  machinery spaces Access to the arresting gear machinery room Access to the eductor room 7-16