（Question on how to interpret Table 3.8.A Corrosivw Material.）
Q.
I refer to Table 3.8.A Class 8 Packing Group Assignment. How do we read the Table? Do we consider both factors, i.e. Exposure Time and Observation Time when assigning the PG? For example, if the Exposure Time is 2 min and the Observation Time is 10 days. Based on the Exposure Time of 2 min, it will be in PG I, and from the Observation Time, it is PG II or PG III. Do we assign it as PG I as it has a higher degree of hazard? (31 Jan 20)
A.
When interpreting Table 3.8.A, you will consider both the Exposure Time as well as the Observation Time. The example you have mentioned with an Exposure Time of 2 min and an Observation Time of 10 days is hypothetical and unrealistic. If an irreversible damage happens with a contact of only 2 min, with such a sensitive substance, you will not have to wait 10 days to witness a damage.
With such a substance, the negative effect will be obvious in a matter of seconds. When interpreting Table 3.8.A, the principle is that if a short contact produces an irreversible damage in a short period, that substance is considered to have a major potential hazard, i.e. PG I. If the substance produces an irreversible damage after a longer observation period following a longer contact time, the degree of hazard is lower, i.e., PG II or even as low as PG III.
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