As i saw in a document, Fo is calculated by considering D value in equations. For example the equation is written as Fo=1/D*(10^T-121.11/z)*∆t.

But in some documets the equation doesn’t have D value. The usage of D value creates some questions, such as;

1)Does Fo have a unit? (minute?)

2)When i put D value in equation, Fo value is effecting very much and so the kill time change dramatically to reach the determined Fo value.

For example, if i use D value in equation and take D value as 2 min, Fo value becomes the half of the Fo value when D value is 1 min.

But most of the documents say that there is no D value in Fo calculation equation.

Up to today, i had been entering the D value to validator, but as i heard from other pharmaceutical companies they neglects the D value and let the validator calculate Fo without any D value.

The BI strips i use in autoclave qualifications, has 2 min D value. In such situation, should i enter the D value to validator or just let the validator works without a D value?