Microbial Contamination Monitors

Vaporized Hydrogen Peroxide VHP Resistance Testing for IsoAir Particle Counters

Vaporized Hydrogen Peroxide is a strong oxidizing agent and has been proven as a sterilizing agent in enclosed filling isolators for many years. As the increase of applications using isolators increases, so does the need for robust sensors capable of withstanding these environments. IsoAir® Pro Remote Particle Sensors contain an internal flow path that is designed to be resistant to the harmful effects of VHP.

Typically, particle counters subjected to VHP vapors cause a bleaching of the internal optical surfaces, resulting in an excess of scattered light from the laser source. To address this issue, the sensor’s optical surface coatings was tested in both static conditions and full VHP cycling tests where the instrument is in operation. Results were analyzed at each phase and the results compared with the specifications given in ISO 21501-4:2018. All results were found to be within tolerance. The IsoAir Pro instruments are suitable for use in a VHP isolator environment.


The 2 tests that were conducted were:

  1. A 1-year typical operation
  2. A 1-year simulated component surface test

All testing methods were designed to test the flow path of the IsoAir Pro instruments, not the external enclosure made of stainless steel. The focus of testing was designed to demonstrate the flow path’s material of construction, including the inlet jet, optical block, collection mirror and diode surround. The stainless-steel enclosure is rated at IP65 and provides protection of the internal electronic. No damage to these components was noted during post testing analysis.

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