Appendix 1 - Ventilation of Ro-Ro Cargo Spaces – Air Quality Control and Management System
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1515 - Revised Design Guidelines and Operational Recommendations for Ventilation Systems in Ro-Ro Cargo Spaces - Appendix 1 - Ventilation of Ro-Ro Cargo Spaces – Air Quality Control and Management System

Appendix 1 - Ventilation of Ro-Ro Cargo Spaces – Air Quality Control and Management System

1 General

This appendix gives directions for measuring the quality of air and to regulate the air flow accordingly. This system is called air quality control.

Air quality control may be used as an instrument to regulate the air flow in closed vehicle spaces, closed ro-ro and special category spaces.

Air quality control is based on measurement of CO, NO2 and LEL values. Based on the measured values the amount of air can be regulated by changing the number of revolutions of the supply and/or discharge ventilators.

2 Requirements

2.1 Monitoring frequency and the resulting response of the ventilation system on air quality in the ro-ro spaces should be sufficient to keep the concentration of flammable and harmful gases below limits.

2.2 Maintenance provisions should be provided by the manufacturer and indicate at least frequency of testing and adjustment of the sensors.

2.3 The system should be capable of automatic operation, with a manual override.

2.4 The power supply, sensors and control equipment should be monitored. An alarm should be generated upon failure, including the manual override.

2.5 Upon any failure in the system including power failure of the control system, the ventilators should switch to the capacity as required in SOLAS regulation II-2/20.3.1.1.

2.6 Maximum section size for sensor equipment should be one hold.

2.7 Periodic onboard test and calibration of sensors should be according to the manufacturer's instructions.

2.8 Alarms as provided in paragraph 2.4 should be sufficient and indicated in the space where the controls for the power ventilation serving the vehicle decks are located on the navigation bridge.footnote

2.9 Gas detection equipment including wiring should be fit for ro-ro cargo hold conditions and meet the relevant standards.

2.10 When CO, or NO2, or concentration of flammable gasses (LEL) exceeds the threshold concentration, an audible and visual alarm should be given at a continuously manned location.

2.11 The control system should be continuously powered and should have an automatic changeover to a standby power supply in case of loss of normal power supply.

3 Air quality control systems

3.1 Air quality control is a system to ensure flammable and hazardous gas concentrations are kept below prescribed levels.

3.2 In ro-ro cargo spaces the following gases should be monitored and managed in order to limit the concentration of harmful exhaust gases when vehicles are being loaded and unloaded, and prevent the build-up of flammable gases while the ship is at sea:

  • .1 for gasoline powered vehicles, carbon monoxide (CO);

  • .2 for diesel engines nitrogen oxide (NO2); and

  • .3 the Lower Explosion Limit (LEL).

3.3 Factors to be taken into consideration when determining what type of system should be specified:

  • .1 Size of space to be monitored: In areas comprised of dividers, sections, corners and other barriers to free movement of air should be condensed to one sensor per 900 m2. Lesser number of sensors may be accepted based on calculations or measurements of the response time on air quality in the holds.

  • .2 Sensor Placement: When installing sensors in a space, care should be taken to keep them away from areas which may have an effect on readings. These include overhead doors (entrances and exits) as well as areas close to the outside air intake or exhaust fans.

4 Minimum quantity of air based on measurements of CO, NO2 and LEL

4.1 Ventilators should be controlled by the air quality control system in order to provide the appropriate number of air changes to restore the normal values of CO, NO2 and LEL as soon as those levels are exceeded during 5 minutes. The ventilation regime should be continuously regulated in relation to the increase of gas concentration and to restore normal levels of CO or NO2 as soon as possible.

4.2 Alarm should be given when the level exceeds 40 mg/m3 CO or 4 mg/m3 NO2 long-term exposure according to the standard ISO 9785:2002 or when a relative concentration of the atmosphere to the LEL is higher than 10%. Other more stringent exposure limits may be used when determined by the Administration, taking national/local occupational regulations into account.

4.3 The minimum amount of ventilation should give sufficient flow for the measurement devices to operate.

5 Detection of CO, NO2 and LEL

The installation and location of the detectors is dependent on the air flow in the holds. To assess the location and number of detectors, the flow of air in the hold should be taken into consideration. In any case, the detectors should be installed to provide the performance required in paragraph 3 and as indicated below:

  • .1 suitable height above deck according to the instruction of the manufacturer;

  • .2 such that each detector covers max 900 m2. Lesser number of sensors may be accepted but with sufficient response time to keep the concentration of harmful gases below exposure and flammable limits; and

  • .3 in accordance with paragraph 3 of part 2 of this guideline and with the manufacturer's instructions concerning sensor placement.

6 Approval Test

A test on board to verify the performance of the air quality control systems according to these guidelines should be performed. Real scale tests may be replaced by model tests to the satisfaction of the Administration.

Parent topic: MSC.1/Circular.1515 - Revised Design Guidelines and Operational Recommendations for Ventilation Systems in Ro-Ro Cargo Spaces
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