We recently got a new freezer for the Blood Bank. I am performing my first validation. I am comparing the NIST against the digital display as well as the chart and our own, seperate thermometer. I cannot find any documentation to support how much difference is acceptable between the NIST and the digital read/our thermometer/ etc. Some places I have read say 0.5 degrees which seems very tight to me. Another facility I work for uses 1.0 degree difference which seems more acceptable and able to obtain but I have not found any supporting documentation anywhere!

Can someone help me? When validating, what difference is acceptable between the NIST and the other thermometers, be it the probes in the unit or your own internal thermometers?

We use 1.0 degree.

1 hour ago, mollyredone said:

We use 1.0 degree.

Do you really read freezer temps to a tenth of a degree?  A typical freezer temperature recorder chart cannot be read to a tenth of a degree nor can a refrigerator temperature recorder chart be read to a tenth of a degree.

Edited February 16, 20178 yr by Dansket
modified sentence

I use 1C as the standard for temp checks, however when I validated a new ultra-low the manufacturer stated that a 2C difference was acceptable.

15 hours ago, Dansket said:

Do you really read freezer temps to a tenth of a degree?  A typical freezer temperature recorder chart cannot be read to a tenth of a degree nor can a refrigerator temperature recorder chart be read to a tenth of a degree.

Yes, the digital temperature readout, which is also calibrated, does read out to 0.1 degrees.

I just validated a new freezer.  Our Biomed performed the NIST to digital check, but I use 1C as acceptable. 

Within 1 degree at in our institution.

We use within 2 C for our freezers, and within 1 C for room temps and refrigerators.

Whatever you use, you must be able to show that whatever you use for documentation (recorder charts or logs), are going to be in compliance within that variance.  

Scott

I used 2 C for the ultra low as recommended by the manufacturer.

The chart on our freezer is in 2 C increments, so we use 2C difference.

We also use within 2 C for our freezers, and within 1 C for room temp and refrigerators.