520. Precautions to prevent pressurisation of certain vessels.

520.     Precautions to prevent pressurisation of certain vessels.

The user1 of a vessel:

  1.  

    (1)     which is constructed with a permanent outlet to the atmosphere or to a space where the pressure does not exceed atmospheric pressure; and

  2.  

    (2)     which could become a pressure vessel if that outlet were obstructed,

must ensure that that outlet is at all times kept open and free from obstruction when the vessel is in use2.