Hold time and FH value for DHS

Dear All,

kindly help to know, how to decide the hold time and FH value acceptance criteria for new DHS. [ As per my knowledge incase of autoclave we decide the hold time = Log reduction required * D-value, and may consider some safety factor].


Minimum FH value should not be less than 24 minutes, when D Value is 2 minutes & Z value is 20°C, but the acceptance criteria should be based on the calculation of the value for the Biological indicator spore strip, which will be used during the Bio-challenge studies. (Biological should be selected as close as possible to the selected hold period).

The calculated FH value should not be less than the biological FH value at all temperature mapping locations for the sterilization hold period.

•Record the temperatures at all Temperature mapping probes during the sterilization hold period.
•Calculate the FH value at each Temperature mapping probe by using the equation given below.
•Record the FH values accordingly based on the type of study conducted.
•Compile the data generated during the qualification test for complete evaluation of the system.

Thanks a lot sir,

but I want to know in case of depyrogenation in DHS what will be the hold time.
( For depyrogenation we challange 3 log for endotoxins) Plz give reference if any.



Dear Akhilesh,

In case of DHS the min. hold time is 250 degC for 3hrs & it depend on your chamber size. But generaly in Industry the time period is 180 min at 300 to 320 degC