2.2 Pressure boundary

 All materials used in the pressure hull, all welding materials and procedures, the design criteria, permissible stresses and all test procedures should comply with the requirements of a recognized organization to the satisfaction of the Administration.

  2.2.2.1 The number and location of access hatches should be subject to special consideration of the Administration, bearing in mind the length of the passenger submersible craft, the length of the pressure hull, the number of passengers, the conditions of operation and rescue facilities.

  2.2.2.2 The following should be taken into account when determining the number, size and location of access hatches:

• .1 access hatches have an essentially important function when passengers and crew must be evacuated in an emergency situation;

• .2 hatches should be arranged with consideration given to all relevant risks such as fire, smoke, hydrostatic stability of the craft after passenger movement, possible down flooding due to adverse sea state, etc.; and

• .3 the number of hatches should not be unnecessarily increased beyond the safe minimum.

  2.2.2.3 Two means, one of which should be visual, should be available to ensure that hatches are closed and secured prior to diving.

  2.2.2.4 Means should be available to ensure that hatches are clear of water before opening, and that pressures on either side of the hatch are equalized. Hatches should be outward opening.

  2.2.2.5 The means for opening and closing of hatches should permit operation by a single person in all anticipated conditions.

  2.2.2.6 Provisions should be made for opening/closing hatches from both sides.

  2.2.2.7 Hatches should have means for securing them in the open and closed position.

  2.2.3.1 Viewports should be of acrylic material and in accordance with the requirements of a recognized organization to the satisfaction of the Administration. Viewports may be of other material, as appropriate, provided viewports of such material are at least as effective and in accordance with the requirements of a recognized organization to the satisfaction of the Administration.

  2.2.4.1 The material of pressure containers should comply with the standards of a recognized organization to the satisfaction of the Administration.

  2.2.4.2 Gas containers should have reliable protection against mechanical damage. They should be securely stowed. The volume of a single internal source should be limited in such a way that complete release of its contents will not increase the pressure beyond the safe limit for the craft and its occupants.

  2.2.4.3 Cylinders and pressure vessels mounted externally which may be depleted while at depth should be designed to withstand external pressures equal to the design depth of the passenger submersible craft.