On the 15th I started a purge on one of the oldest, and least purged ISIs we have. The LN2 boil-off straight from the dewar was measuring ~ -40 td°C, while ambient air was ~ -5 td°C. This unit was taking longer than usual to dry out and wasn't reaching as low of levels as other containers had in the past. I think revisiting Assy. 1 soon would be helpful.