CIRCLE WILLIAM fittings are marked with a black W inside a black circle. These fittings are normally kept open, as is the case with WILLIAM fittings. They must, however, be secured to prevent the spread of damage and as a defense measure when a CBR attack is imminent. You will find this classification on the following closures:

. Doors to the pilot house, flag bridge, and signal shelter 

l Ventilation systems to main and auxiliary machinery spaces, generator spaces, and other systems and fittings serving spaces in continuous use

If access to a space is through a series of hatches and/or scuttles, all of the closures that provide that access must bear the same classification as that of the space. For example, a pump room is classified as CIRCLE YOKE. This means it is open during condition XRAY and closed during condition YOKE. All hatches, scuttles, and/or doors that provide access to the pump room must also be classified CIRCLE YOKE to allow routine access to the pump room.

When a fan room door must be kept open to supply air to a fan or to exhaust air from it, the door should have the same classification as that of the fan. For example, a fan room containing a YOKE fan has a YOKE door; a room containing YOKE and ZEBRA fans has a ZEBRA door. All other fan room doors are classified XRAY.

A classification has no bearing on the security of a space. A space classified ZEBRA may, for security reasons, be locked during condition YOKE if the space is unattended. However, the locking must be reported to the damage control assistant (DCA) or to the OOD.

Table 3-2 has additional information on damage control closures and classifications.

When material conditions of readiness are being set, the ship's first concern is the requirement for watertight, airtight, firetight, and fumetight integrity. Living conditions and access to spaces are secondary requirements. During long periods at general quarters stations, however, condition ZEBRA may, with the commanding officer's permission, be relaxed to pass battle rations and to allow the crew to use the head facilities. The opening of certain weather deck doors permits natural ventilation to replace the stuffiness at some general quarters stations with fresh air. Condition YOKE may also be modified in a similar manner when appropriate.

Table 3-2.-Damage Control Classifications

Table 3-2.-Damage Control Classifications-Continued

Table 3-2.-Damage Control Classifications-Continued

Table 3-2.-Damage Control Classifications-Continued