# Performance qualification of dry heat sterilization

Dear all,

I have a question about FH value of sterilizing dry heat.

According to Chapters: <1229.8> DRY HEAT STERILIZATION in USP
For the specific reference temperature of 170 and a z-value of 20, the FH (reality) calculation can be determined by the following equation:
FH = ΔT x Σ10^[(T − 170) / 20]

I want to ask: What is the acceptance criteria for FH?

The biological indicator (BI) that I used to have the population N = 2.1x10^6 and d-value of 1.3 at 170.
I hope you can help me to resolve this problem.

what is the hold time are u folowing ?
Generally lithality shll be not less than Hold time.

Dear Prachi1, I’m following the cycle 180oC/1 hour (the Hold time = 30 min), but the FH (theory) calculation = 16 min (FH (Theory) = D*(Log(N)-Log(N0)) = 1.3*(Log(2.1*10^6)-Log(10^-6)) = 16 min). When I calculate FH (reality) = 98 min
I hope you can help me to explain this problem clearly.

I think you have to reduce your hold time
its may be like 180oC for at leats 10 min so you can get physical lithality around 30 min.
Fphy = ΔT x Σ10^[(T − 170) / 20]
= 10 x Σ10^[(180 − 170) / 20]
= 31.62
F bio = D*(Log(N)-Log(N0))
= 1.3*(Log(2.110^6)-Log(2.110^-6)) = 16.43 min.

Dear Prachi1, Fphy = ΔT x Σ10^[(T − 170) / 20 = 10 x Σ10^[(180 − 170) / 20] = 10 x (3.162+3.162+3.162) = 94.868
I think You mistook for above calculation. Thank you