How Can We Put 3 Minutes Hold Time for Depyrogenation Tunnel During Tunnel Validation

How can we put 3 minutes hold time for Depyrogenation tunnel during Tunnel validation.Is there any rationale for that?USP is saying 30 minutes at 250 deg.centigrade for depyrogenation process.How come the hold time has reduced to 3 min at 50 degrees variation?Anyway we will challenge with spiked endotoxin vials.But before validation how come we fix the hold time?

Please refer to twebsite below.,M1

Hello !
The Z value for the calculation of the lethality in tunnel is is considered as 46.4 degree cent. Hence the change in the temperature by 46.4 degree centigrade will change the lethality by one log i.e. the increase in temperature about 46.4 °C it will cause change of one log in the time i.e. 30 minutes to 3 minutes.

Please feel free to communicate if you have any furthur query.


Dear Anil

Does the Z value remains 46.4 even if we are considering 250 deg. for sterilzation & depyrogenation.

Also while validating the tunnel we have considered the Z value of 46.4 and temp of 300 deg. and we are achieving the required temp for more than 3 min at individual temperature probe during sterilization.

Is it mentioned somewhere that FH obtained by these criteria should be equivalent to the exposure time i.e 3 min. pls. clear it to me that if our study meets the acceptance criteria or not

can you define exactly what 1 log means and can you provide any reference for the information you have given

yup you are correct but if we increase temperature by Z Value then our D value will decrease by factor of 10 but not the lithality and the endotoxin will not have the D value and population it have the Endotoxin Unit .the concept you told may relates to moist heat not depyrogenation or dry heat