A vessel was undergoing a periodical survey by a DNV class surveyor. A total of 19 air vent heads (mostly from ballast tanks) were found to be defective and the surveyor requested the master to repair this before leaving port. This example is taken from a DNV case but defective vent heads (sometimes also called air pipe closing devices) are frequently found in ship surveys, so this example is by no means unique.
Officer of the Watch 