Pressure Decay Test is also known as the pressure hold
test. During the test, a high-precision pressure gauge or
sensor is used to monitor the pressure change caused
by the diffusion of gas leaking or passing through the
filter. This test has two main uses:
1. to measure the tightness of the filtration system
2. detect filter integrity
3.Tests Principle Integrity Testing
Tests principle Integrity testing methods including diffusion flow test, bubble point test, pressure hold
test, water flow test and enhanced bubble point test in accordance with 21 CFR Part 11. The Integrity
Tester is also complied with the standard requirements of Pharmaceutical Industry.
Tests Principle Integrity Testing
At a certain temperature, the minimum pressure difference
required to vent the largest hole in the wetted filter
membrane is forced by gas.
Bubble Point Test
a. Bubble Point Test
b. Bubble Point Definition
D：
θ：
γ：
the diameter of the largest pores
the contact (“wetting”) angle between the liquid and
the membrane
the surface tension of the wetting liquid
k：correction factor for the shape of the largest pores
P = 4× kcos
D
γ
θ
Pressure
Bubble point
Membrane Membrane MembraneMembrane
× ×
b. Diffusion Flow Definition
Diffusion Flow Test
a. Diffusion Flow Principle
Diffusion Flow refers to the flow of gas through the
pores of the membrane hole driven by a pressure
difference between compressed air and nitrogen on
both sides of the membrane at a pressure below the
bubble point.
The bubble point test is a non-destructive test method
based on the principle of surface tension and capillary
phenomena of liquid in the pores of the filter membrane.
The bubble point detects the minimum pressure
required to overcome these forces and expel the liquid
in the pores of the membrane.
Q = K×H(P1-P2)×R
L
Pressure
Gas molecule
Diffusion
Membrane
Q：
K：
H：
Diffusion Flow (throughput per unit time)
membrane-specific correction factor
Henry's law coefficient 1
P1：
R：
L：
inlet side pressure
ideal gas constant
length of diffusion path
P2：outlet side pressure
- 6 - - 7 -
Water Flow Test
a. Water Flow Principle
The water flow method complies with the FDA's
integrity testing requirements for sterilizing grade
filters. It can be associated with bacterial challenge
experiments. The water flow test is a highly sensitive
method of performing hydrophobic membrane
integrity testing based on water flow without alcohol.
Since the filter is not wetted and is almost dry, it can be
blown (baked) after the integrity test is completed and
put into use.
Pressure Decay Test
a. Pressure Decay Principle
The diffusion flow test can also be approximated by
measuring the pressure decay of the filter. After a
certain period of time, the attenuation value can be
measured to determine the integrity of the filter.
Calculated as follows:
b.Water Flow Definition
The minimum pressure difference between the
maximum pores of the hydrophobic membrane.
(In general, the water flow value is tested by
means of constant pressure water flow, similar
to the diffusion flow test),
△P × V
DF = Pa × T
Pressure
Water molecule
Hydrophobic membrane
DF：diffusion flow (ml/min)
pressure decay (mbar)
upstream volume (cm³)
atmospheric pressure (1013 mbar)
test time (min)
△P：
Pa：
T：
V：
△P × V
WFT = Pa × T
WFT：water flow test (ml/min)
pressure decay (mbar)
upstream volume (cm³)
atmospheric pressure (1013 mbar)
test time (min)
△P：
Pa：
T：
V：
CF 7.2IntegrityTester Instruction ManualCF 7.2IntegrityTester Instruction Manual
Recommend temperature: 20+/- 5 oC.
Temperature shifts must be avoided during the measurement.
Recommend temperature: 20+/- 5 oC.
Temperature shifts must be avoided during the measurement. Recommend temperature: 20+/- 5 oC.
Temperature shifts must be avoided during the measurement.
Recommend temperature: 20+/- 5 oC.
Temperature shifts must be avoided during the measurement.
