Artikel 20

(1) In vessels of 45 metres in length and over, the height above deck of ventilator coamings, other than machinery space ventilator coamings, shall be at least 900 millimetres on the working deck and at least 760 millimetres on the superstructure deck. In vessels of less than 45 metres in length, the height of these coamings shall be 760 milimetres and 450 millimetres 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 millimetres in height it shall be specially supported.
(3) Closing appliances in vessels of 45 metres in length and over need not be fitted to ventilators the coamings of which extend to more than 4.5 metres above the working deck or more than 2.3 metres above the superstructure deck unless specifically required by the Administration. In vessels of less than 45 metres in length, closing appliances need not be fitted to ventilators the coamings of which extend to more than 3.4 metres above the working deck or more than 1.7 metres 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.