Leakage percentage with the ATI Photometer

Dear all:

I hope you will help me with this question.
I have been trying different ways to set the 100% of leakage with the ATI photometer, I have used it in Hepa Terminal Filters and laminar flow cabinets, but I’m not sure about my data.
How could I set a repeteable 100% of leakage, to have a stablished data for every filter and cabinet, to trace if those are working or not?

I’m looking forward to read your answers

Dora Moro