In first instance, the intention was to replace the three existing tests, i.e. the Dutch PVT (UN E.2), the US PVT (UN E.3) and the Japanese PVT (not in the UN Manual), by one closed PVT. Two tests were candidate for further development：
- the Modified Thermal Explosion Vessel Test (formerly UN test E.5),
- the Modified Closed Pressure Vessel Test (proposed by Japan).
First meeting
Both proposed test methods (MTEVT and MCPVT) are closed vessels, while the existing tests are vented tests. During the discussions within the working group, it appeared that this difference caused a major constraint in the development of a new test method.
For instance, a closed pressure vessel test may underestimate the hazard when volatile solvents are present. Also, it is doubtful whether a test in a closed pressure vessel will be able to reflect the current classification of organic peroxides due to the higher confinement in the test. It may therefore be necessary to maintain an open PVT in test series E.
On the other hand, the closed pressure vessel test is equipped with devices for measuring the pressure and the temperature, which will provide much useful information on the behaviour of the material under investigation. This information can also be useful in view of the globally harmonised system, e.g. for production. It can therefore be wise to include a closed PVT in the UN Manual, e.g. as a screening procedure.
Concerning the choice of a closed PVT, the working group extensively compared the merits and drawbacks of both methods and it was agreed that the Modified Closed Pressure Vessel Test (MCPVT) was a better candidate. For instance, the MCPVT is commercially available and has a better heating system.
Available test results from the MCPVT indicate that this test could form the basis of a good screening test, not only for test series E, but also for other test series.
The working group decided that：
- the MCPVT apparatus needed to be standardised,
- other laboratories will consider purchase and participation in round-robin testing,
- a join Netherlands/Japan document will be submitted to the UN at the end of the biennium,
- in 1998/1999 round-robin tests will be performed to assess the effectiveness of the procedure, the reproducibility and to agree suitable criteria,
- in 1999/2000 the MCPVT would be proposed for inclusion as a screening procedure,
- if experience shows that the MCPVT can be used for classification, a full procedure will be proposed in a later stadium.
Since at that time nearly all experience with the MCPVT was concentrated in Japan and the United Kingdom, experts from these two countries agreed to co-ordinate the work.
