To improve the quality of the air at the workplace knowledge
must be gained of how the pollution from the vehicles is diffused
through the air in the ro-ro cargo space.
Visual tests using visible smoke do not provide any direct readings
of the rate of air change or air distribution in a ro-ro cargo space,
although they often provide sufficient indication of a satisfactory
picture to be obtained of the air circulation, the existence of any
stagnant or screened zones and the rate at which pollutants are removed
by the ventilation system.
The visible smoke method is
simple and can readily be carried out by the officer responsible for
ro-ro cargo space ventilation.
The use of tracer gas will
give a more reliable picture of air changes and the air circulation
in the ro-ro cargo space. However, the procedure for using tracer
gas is more complicated. As the same measurement points are used,
it is expedient to use tracer gas in combination with stationary monitoring
of pollutant concentration in a ro-ro cargo space.