Entry to freight containers represents a significant hazard to staff responsible for inspection, stuffing or destuffing because of the large number of airborne chemicals that can be present. Research in Germany and the Netherlands found hazardous levels of gases and vapours in around 20% of all containers, so a multiparameter gas analysis technology (FTIR) is being used very successfully to check the safety of the air inside containers.
Traditionally, gas detection has been conducted with a wide variety of techniques to assess, individually, all of the substances of greatest concern. However, FTIR (Fourier Transform Infra-Red) gas analysis has dramatically improved the speed and effectiveness with which containers are assessed, because this technology enables the simultaneous measurement of the 50 gases of most concern in about 3 minutes.
Containers often travel for extended periods and experience a wide range of temperatures. It is therefore unsurprising that unsafe levels of gases should accumulate in the confined space of a container and there are two potential sources; fumigants and chemicals that arise from the goods or packing materials.
In an attempt to measure the large number of gases that might be present, the traditional approach has been to employ a wide range of instruments, or to use chemical stain tubes for the most common gases, or a combination of both.
Chemical stain tubes provide a colorimetric assessment of an individual gas, typically with an accuracy of +/- 15% or worse. Different tubes are available for many gases and results can be obtained between 5 seconds and 15 minutes, depending on the test. Once a result has been obtained, the tube itself is hazardous waste and must be disposed of. Historically, stain tubes have been popular because the cost per test is low. However, the number of tubes that have to be employed in order to demonstrate that a container is safe can be prohibitively expensive and time-consuming.
Instrumental gas analysers, such as electrochemical sensors that measure either a single gas or a small number of gases, impart a similar level of risk to stain tubes because of the possibility of missing or failing to measure a harmful gas. Deploying multiple instruments also presents practical problems because each will require maintenance and re-calibration.
Users in Holland have developed a configuration for the portable FTIR (a Gasmet
DX4030) that measures the 50 compounds of greatest concern. As a result, they are now able to test for all of these gases in around 3 minutes, which dramatically lowers the time taken for container inspection and greatly increases the number of containers that can be examined every day.
A further major advantage of this technology is the minimal amount of calibration and maintenance that is necessary. A new instrument can be delivered pre-configured and factory calibrated and from then on the only calibration required is a quick zero check with nitrogen once or twice per day. As a result, it is not necessary to transport a large number of expensive, bulky calibration bottles.
Portable FTIR is currently being utilised by freight companies that conduct their own testing and by testing staff at ports in Rotterdam, Amsterdam, Vlissingen, Antwerp and Hamburg.
Millions of containers arrive in international ports every year and it is clear that a large proportion of them represent a significant hazard. Employers have a duty of care to protect their staff and court cases have found in favour of workers that have suffered ill-health from container gases. It is inevitable therefore that the amount of testing required will continue to increase so there will be a greater emphasis on speed, risk reduction and cost.
In summary, portable FTIR gas analysers substantially reduce the amount of equipment required to test a container, but more importantly, the technology enables the simultaneous analysis of a large number of target compounds, which improves the effectiveness of the assessment and reduces risk to staff. The technique is also much faster and avoids the use of disposable equipment.