That Darned Ultra-Freezer!

During an extensive launch of a biologics study we had the door of our reach-in ultra-freezer open about 15 times in 45 minutes. As expected, during that 30 minutes the temperature rose from -80°C to -34°C, which was similar to what we saw during the open-door test while requalifying the chamber two years ago. No other product was in the unit, so we weren’t concerned about the temporary rise in temperature. Unexpectedly, though, it took nearly 19 hours for the unit to return to -70°C—the upper end of the -80° ±10°C setpoint—even though the material we placed in the chamber was already at -80°C, having come right from the cold-storage warehouse.

My “mistake” was that out of cautious curiosity I checked the qualification packet and confirmed that the unit had performed much more robustly during the open-door test. In that test the door was left open for 15 contiguous minutes and the temperature climbed to -38°C but returned to -70°C in only 4 1/2 hours versus the predetermined requirement that it come back in range (-70°C to -90°C) within 8 hours. Unfortunately, I now know something that I don’t want to know, that this unit does not appear to be running as well as when it was qualified, but it’s holding temperature just fine now.

My manager came up with these three options:

1. Open an exception document (investigation/deviation) to determine root cause and impact, such as on other studies held in this chamber last year.

2. Do nothing and just wait one more year till our routine tri-annual requalification and maybe initiate an exception document based on those findings (if it is, in fact, misbehaving).

3. Move the material to another unit and only document the move in the chamber log, then have the HVAC group determine if it needs to be repaired.

What would you recommend? Do you have another option that's even better? We want to hear your thoughts.