[Code of Federal Regulations]
[Title 46, Volume 7]
[Revised as of October 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 46CFR171.066]

[Page 126-127]
 
                           TITLE 46--SHIPPING
 
   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)
 
PART 171--SPECIAL RULES PERTAINING TO VESSELS CARRYING PASSENGERS--Table of Contents
 
                        Subpart C--Large Vessels
 
Sec. 171.066  Calculation of permeability for Type I subdivision.

    (a) Except as prescribed in paragraph (b) of this section, the 
following permeabilities must be used when doing the calculations 
required to demonstrate compliance with Sec. 171.065(a), (b), and (c):
    (1) When doing calculations required to demonstrate compliance with 
Sec. 171.065(a) and (b), the uniform average permeability given by the 
formulas in Table 171.066 must be used.
    (2) When doing calculations required to demonstrate that 
compartments on opposite sides of a main transverse watertight bulkhead 
that bounds the machinery space comply with Sec. 171.065(c), the mean of 
the uniform average permeabilities determined from Table 171.066 for the 
two compartments must be used.
    (b) If an average permeability can be calculated that is less than 
that given by the formulas in Table 171.066, the lesser value may be 
substituted if approved by the Commanding Officer, Marine Safety Center. 
When determining this lesser value, the following permeabilities must be 
used:
    (1) 95% for passenger, crew, and all other spaces that, in the full 
load condition, normally contain no cargo, stores, provisions, or mail.
    (2) 60% for cargo, stores, provisions, or mail spaces.
    (3) 85% for spaces containing machinery.
    (4) Values approved by the Commanding Officer, Marine Safety Center 
for double bottoms, oil fuel, and other tanks.
    (c) In the case of unusual arrangements, the Commanding Officer, 
Marine Safety Center may require a detailed calculation of average 
permeability for the portions of the vessel forward or aft of the 
machinery spaces. When doing these calculations, the permeabilities 
specified in paragraph (b) of this section must be used.
    (d) When calculating permeability, the total volume of the `tween 
deck spaces between two adjacent main transverse watertight bulkheads 
that contains any passenger or crew space must be regarded as passenger 
space volume, except that the volume of any space that is completely 
enclosed in steel buldheads and is not a crew or passenger space may be 
excluded.

         Table 171.066--Table of Uniform Average Permeabilities
------------------------------------------------------------------------
                 Location                   Uniform average permeability
------------------------------------------------------------------------
                                             10 (a-c)
Machinery space...........................  85+----------
                                             v
-------------------------------------------
                                             35(a)
Volume forward of machinery space.........  63+------

[[Page 127]]


                                             v
-------------------------------------------
                                             35(a)
Volume aft of machinery space.............  63+------
                                             v
------------------------------------------------------------------------
For each location specified in this table--
a=volume below the margin line of all spaces that, in the full load
  condition, normally contain no cargo, baggage, stores, provisions, or
  mail.
c=volume below the margin line of the cargo, stores, provisions, or mail
  spaces within the limits of the machinery space.
v=total volume below the margin line.


[CGD 79-023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 88-070, 53 FR 
34537, Sept. 7, 1988]