(1) In vessels of 45 m in length and over, the
height above deck of ventilator coamings, other than machinery space
ventilator coamings, shall be at least 900 mm on the working deck
and at least 760 mm on the superstructure deck. In vessels of less
than 45 m in length, the height of these coamings shall be 760 mm
and 450 mm respectively. The height above deck of machinery space
ventilator openings shall be to the satisfaction of the Administration.
(2) Coamings of ventilators shall be of equivalent
strength to the adjacent structure and capable of being closed weathertight
by closing appliances permanently attached to the ventilator or adjacent
structure. Where the coaming of any ventilator exceeds 900 mm in height
it shall be specially supported.
(3) Closing appliances in vessels of 45 m in length
and over need not be fitted to ventilators the coamings of which extend
to more than 4.5 m above the working deck or more than 2.3 m above
the superstructure deck unless specifically required by the Administration.
In vessels of less than 45 m in length, closing appliances need not
be fitted to ventilators the coamings of which extend to more than
3.4 m above the working deck or more than 1.7 m above the superstructure
deck. If the Administration is satisfied that it is unlikely that
water will enter the vessel through machinery space ventilators, closing
appliances to such ventilators may be omitted.