Need to monitor Atmosphere in RO RO ship cargo spaces
Exhaust gases from motor vehicles contain hazardous substances. Carbon monoxide from petrol engines and nitric oxide (NO) & nitrogen dioxide (NO2) from diesel engines are released in the cargo spaces
These hazardous substances can effect people in many different way. Certain substances have a tangible, immediate effect, others only show injurious effects after a person has been exposed to them for some time.
Carbon monoxide is a colourless and odourless gas which, to a lesser or greater extent, inhibits the ability of the blood to absorb and transport oxygen. Inhalation of the gas can cause headaches, dizziness, and nausea and in extreme cases causes weakness, rapid breathing, unconsciousness and death.
Nitric oxide (NO) and nitrogen dioxide (NO2) are compounds of nitrogen and oxygen, together commonly referred to as oxides of nitrogen or NOx. NO itself is not of great concern as regards health effects; however a proportion of the NO formed will combine with oxygen to form NO2, which is of concern from the point of view of human health.
NO2 is a brown gas which has a stinging, suffocating odour. It exerts a detrimental effect on the human respiratory system. Asthmatics in particular are susceptible to exposure.
Measures
Therefore measures should be considered to minimize the health hazards. Such measures could include :
1. A reduction in exhaust gas emissions.
2. Provision of an adequate ventilation system
3. Prevention of exposure to the gases
To ensure the effectiveness of above recommended measures, it is essential that the atmosphere in the RO RO vessels is monitored.
Additional Information
Ventilation system for ro ro cargo spaces on board ship generally operate according to the principle of dilution ventilation, where by the supply air flow to the area is sufficient for the exhaust gases to mix thoroughly with the air and be removed.
There are two main types of dilution ventilation: exhaust air ventilation and supply air ventilation.
In exhaust air ventilation, fans remove air from a ro-ro cargo space and this is then replaced by outdoor air entering through open ramps, doors and other openings.
Exhaust air ventilation is employed when sub-atmospheric pressure is required in the ro-ro cargo space. The sub-atmospheric pressure prevents the pollution from spreading to adjacent areas.
Supply air ventilation works in the opposite way. Fans deliver outdoor air into the ro-ro cargo space and the air is then exhausted through ramps and other openings.
Supply air ventilation usually creates slight pressurisation of the ro-ro cargo space. If supply air ventilation is used exclusively, pollutants may mix with the supply air, be pushed up the internal ramps and contaminate other decks. However, if sufficient mixing with supply air does not occur, contaminants may remain on the deck in question.