Section 2 Ventilators

2.1 General

2.1.1 Ventilators located on the exposed deck over the forward 0,25L of the rule length, of ships of sea-going service of length 80 m or more, where the height of the exposed deck in way of the item is less than 0,1L or 22 m above the summer load waterline, whichever is the lesser, are to comply with the requirements of Pt 3, Ch 12, 5 Air pipes, ventilator pipes and their securing devices located on the exposed fore deck. All other ventilators are to comply with the following requirements.

2.1.2 Special care is to be taken in the design and positioning of ventilator openings and coamings, particularly in the region of the forward end of superstructures and other points of high stress. The deck plating in way of the coamings is to be efficiently stiffened.

2.1.3 Ventilators from deep tanks and tunnels passing through 'tween decks are to have scantlings suitable for withstanding the pressures to which they may be subjected, and are to be made watertight.

2.1.4 For height and location of cargo tank vent outlets, see Pt 5, Ch 15, 4 Cargo tank venting, purging and gas-freeing and see also 8.2 Pressure relief systems .9 and 8.2 Pressure relief systems .10 of the Rules for the Construction and Classification of Ships for the Carriage of Liquefied Gases in Bulk (hereinafter referred to as the Rules for Ships for liquefied Gases), or Ch 1, 8.2 Cargo tank venting 8.2.2, of the Rules for the Construction and Classification of Ships for the Carriage of Liquid Chemicals in Bulk (hereinafter reffered to as the Rules for Ships for Liquid Chemicals), where applicable.

2.2 Coamings

2.2.1 The scantlings and height of ventilator coamings exposed to the weather are to be not less than required by Table 12.2.1 Ventilator coaming requirements but the thickness need not exceed that of the adjacent deck or bulkhead plating. In particularly exposed positions, the height of coamings and scantlings may be required to be increased.

Table 12.2.1 Ventilator coaming requirements

Feature	Requirements
Height (measured above sheathing if fitted)	(1)	z_c = 900 mm at Position 1 (see Pt 3, Ch 1, 6.6 Position 1 and Position 2)
		z _c = 760 mm at Position 2 (see Pt 3, Ch 1, 6.6 Position 1 and Position 2)
Thickness	(2)	t _c = 5,5 + 0,01 δ_v mm where 7,5 mm ≤ t _c ≤ 10,0 mm
Support	(3)	If z _c > 900 mm the coaming is to be specially supported
Symbols
t _c = thickness of coaming, in mm
z _c = height of coaming, in mm
δ_v = internal diameter of coaming, in mm
NOTE Where the height of the ventilator exceeds that given in Item (1), the thickness given by (2) may be generally reduced, above that height, to a minimum of 6,5 mm. The ventilator is to be adequately stayed.

2.2.2 Where ventilators in locations above Position 2 are included in the consideration of intact and damage stability or are in critical locations above Position 2, then the height of ventilator coamings is to be specially considered.

2.2.3 The height of ventilator coamings may be required to be increased on ships of Type `A', Type `B-100' and Type `B-60' where this is shown to be necessary by the floatability calculations required by the Load Lines, 1966/1988 - International Convention on Load Lines, 1966, as Amended by the Protocol of 1988 .

2.2.4 For gooseneck ventilators, the coaming height is to be measured to the underside of the bend, this being the lowest point through which water on deck could pass freely to spaces below.

2.2.5 Where wall vents are fitted with an internal baffle which rises above the lower edge of the exterior opening, the coaming height is measured to the top of the baffle.

2.2.6 Where permitted by the National Authority, ventilator coaming heights may be reduced on ships engaged on protected or extended protected water service. Coaming heights are to be as high as practicable, with a minimum height of 450 mm in Position 1 and 300 mm in Position 2.

2.3 Closing appliances

2.3.1 All ventilator openings are to be provided with efficient weathertight closing appliances of steel or other equivalent material unless:

the height of the coaming is greater than 4,5 m where Table 12.2.1 Ventilator coaming requirements requires a minimum height of 900 mm; or
the height of the coaming is greater than 2,3 m where Table 12.2.1 Ventilator coaming requirements requires a minimum height of 760 mm.

2.3.2 In ships where the load line length, L _L (see Pt 3, Ch 1, 6.1 Principal particulars), is not more than 100 m, the closing appliances are to be permanently attached to the ventilator coaming. Where not so provided in other ships, they are to be conveniently stowed near the ventilator to which they are to be fitted.

2.3.3 Where, in ferries, ventilators are proposed to be led overboard in an enclosed 'tween deck, the closing arrangements are to be submitted for approval. If such ventilators are led overboard more than 4,5 m above the main vehicle deck, closing appliances may be omitted, provided that satisfactory baffles and drainage arrangements are provided, as in the case of air intakes or exhaust openings for machinery spaces, which may be arranged in the sides of the ship.

2.3.4 On offshore supply ships, to ensure satisfactory operation in all weather conditions, machinery space ventilation inlets and outlets are to be located in such positions that closing appliances will not be necessary.

2.3.5 Mushroom ventilators closed by a head revolving on a centre spindle (screw down head) are acceptable in Position 2, and also in sheltered positions in Position 1, excluding those described in Pt 3, Ch 12, 2.1 General 2.1.1, but the diameter is not to exceed 300 mm if situated within the forward 0,25L _L.

2.3.6 Mushroom ventilators with a fixed head and closed by a screw down plate (screw down cover) may be accepted in exposed positions within the forward 0,25L _L, excluding those described in Pt 3, Ch 12, 2.1 General 2.1.1, up to a diameter of 750 mm.

2.3.7 Wall ventilators (jalousies) may be accepted provided they are capable of being closed weathertight by hinged steel gasketed covers secured by bolts or toggles.

2.3.8 A ventilator head not forming part of the closing arrangements is to be not less than 6,5 mm thick.

2.3.9 In order to limit the fire growth potential in every space of the ship, the main inlets and outlets of all ventilation systems shall be capable of being closed from outside the spaces being ventilated. The means of closing shall be easily accessible as well as prominently and permanently marked and shall indicate whether the inlet or outlet is open or closed. Unless required by SOLAS, Chapter II-2, Part C, Regulation 9 - Containment of fire, emergency generator room ventilators need to be fitted with such means of closing, only when the emergency generator room is fitted with a fixed gas fire-fighting system. Battery room ventilators are only to be fitted with a means of closing, whenever:

the battery room does not open directly on to an exposed deck; or
the ventilation opening for the battery room is required to be fitted with a closing device according to the Load Line Convention; or
the battery room is fitted with a fixed gas fire-extinguishing system.

Where a battery room ventilator is fitted with a closing device see Pt 6, Ch 2, 12.5 Thermal management and ventilation 12.5.2. The means of closing mentioned in this paragraph refers to closing appliances of ventilation inlets and outlets for minimising the potential fire growth. The requirements specified are distinct from those for weathertight closing appliances.

2.4 Machinery spaces

2.4.1 In general, ventilators necessary to continuously supply the machinery space are to have coamings of sufficient height to comply with Pt 3, Ch 12, 2.3 Closing appliances 2.3.1 without having to fit weathertight closing appliances. Ventilators to emergency generator rooms are to be so positioned that weathertight closing appliances are not required.

2.4.2 Where due to ship size and arrangement this is not practicable, lesser heights for machinery space ventilator coamings fitted with weathertight closing appliances may be permitted by the Administration in combination with other suitable arrangements to ensure uninterrupted, adequate supply of ventilation to these spaces.

2.4.3 Where closing appliances are fitted as per Pt 3, Ch 12, 2.3 Closing appliances 2.3.9 or Pt 3, Ch 12, 2.4 Machinery spaces 2.4.2, to ventilators serving emergency generator rooms or closable ventilation louvres are used for emergency generator rooms, the following requirements are to be applied in addition to the requirements of Pt 3, Ch 12, 2.4 Machinery spaces 2.4.2:

Ventilation louvres and closing appliances may either be hand-operated or power-operated (hydraulic/pneumatic/electric) and are to be operable under a fire condition. Closing appliances, which automatically close in response to exposure to fire products, are not to be fitted on ventilators located at outside boundaries and serving emergency generator rooms.
Hand-operated ventilation louvres and closing appliances are to be kept open during the normal operation of the vessel. Corresponding instruction notices are to be provided at the location where hand operation is provided.
Power-operated ventilation louvres and closing appliances are to open automatically whenever the emergency generator is starting/in operation. Closed ventilation louvres and closing appliances are acceptable during normal operation of the vessel. In the event of power failure, the default position of the ventilation louvres or closing appliances is to be the open position.
Ventilation openings are to be capable of being operated manually from a clearly marked safe position outside the space where the closing operation can be easily confirmed. The louvre status (open/closed) is to be indicated at this position. Such closing is not to be possible from any other remote position.