Sample Shipment (dry ice) ☣ [GxP / QC / QA]
recently I saw the documentation of a sample shipment from Toronto, Canada to Graz, Austria by World Courier. This is the readout of the sensor placed between the samples:
I was confused at first. –82.0 ℃ though dry ice sublimates at −78.48 ℃?
Then I remembered physical chemistry and looked at the phase diagram of CO2. −78.48 ℃ is correct but only at the standard condition for pressure (101.325 kPa). However, the cabin pressure is much lower (depending on the aircraft down to 74.5 kPa, equivalent to 2,400 m). The 767-300ER is a fairly modern aircraft and – if we trust in the logger – was pressurized to 81.4 kPa (equivalent to 1,700 m). Also the cargo deck generally is not heated. Given that, CO2 sublimates at the ambient conditions, effectively cooling the samples. Riddle solved. The scheduled flight time Toronto → Vienna is 8:35 h. Maybe bad weather or the airspace was crowded causing a delay.
No idea why the temperature went up to –64.5 ℃. Did Austrian customs officers open the box and inspect it for hours?
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