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Section 3 Air Supply
301. Air supply and exhaust system
1. When travelling on the surface, the vehicle is to be ventilated via an air mast which is to be de- signed and arranged to prevent the penetration of spray and swell water.
2. A power driven extractor fan is to be provided for expelling the battery gases and spent air from the vehicle. The venting of battery spaces is to be separated from other ventilation systems.
302. Oxygen removal
1. An oxygen system is to be installed to replace the oxygen consumed from the atmosphere in the vehicle.
2. The oxygen system is to be designed on the basis of a consumption rate of at least 26 ThĤh per person.
3. The oxygen is to be stored in at least two separate banks of bottles, if possible, outside the pres- sure hull.
4. Each bank of oxygen bottles is to be connected to the inside of the vehicle by a separate line.
5. All pipes and components used in oxygen systems are to be carefully cleaned and degreased before being put into service.
6. Manually operated oxygen metering systems are to be equipped with a bottle shutoff valve and a device for controlling the flow rate. A flow rate indicator should be fitted.
7. Metering devices are to be equipped with a manually operated bypass.
303. CO2 absorption
1. For regenerating the breathing air a CO2 absorption unit is to be provided which shall be capable of keeping the CO2 partial pressure in the range 0.005 ~ 0.010 bar. In addition, it shall be possible to maintain a CO2 partial pressure within the vehicle of not more than 0.020 bar at the end of the survival time stated in 201. 1.
2. The design of the CO2 absorption unit is to be based on 2 CO2 production of 22 ThĤh per person at 20°C and 1 bar.
3. The CO2 absorption unit is to be fitted with a dust filter of non-combustible material.
304. Emergency breathing air supply
1. Emergency breathing air systems/appliances are to be designed to ensure that in an emergency all crew members have sufficient breathing air while the submersible is rising, or being brought, to the surface, subject to a minimum time of 30 minutes.
2. The emergency breathing air appliances are to be so designed and arranged that in an emergency each crew member can very quickly reach a breathing appliance and can reach the exit from the submersible without first having to remove the breathing appliance.
305. H2 monitoring
1. The hydrogen content is to be monitored continuously in the battery spaces, the exhaust system and if applicable in other spaces. The position of the measuring points is to be fixed in accordance with the local conditions.
2. If the gas concentration of 35 % of the lower explosion limit is exceeded it is to be signalled opti- cally and acoustically to the control stand. If a value of 50 % of the lower explosion limit is reached, all charging or discharging processes have to be interrupted automatically. If the H2 con- centration is still rising after the enforced switch-off, e.g. from finish gassing of the batteries, im- mediately surfacing is to be initiated and forced ventilation is to be applied.
3. The request for immediate surfacing is to be signalled optically and acoustically at the control stand. Acknowledgment of the optical signal is to be possible only after surfacing and after suffi- cient fresh air has been supplied.
4. The measuring and signalling equipment for monitoring of the H2 concentration are to be type test- ed by the Society.
5. The hydrogen measuring system is also to be supplied by emergency power.
