Vapor Probe (G-SST)

The G-SST Probe was design to be installed directly into a vacuum sterilization chamber for process monitoring. The probe enables reaction chemistry and specific chemical concetrations to be monitored in enviroments where electrochemical sensors cannot not operate. Over the last 25 years, design improvements to the GSST Vapor probe have enabled more precise measurements of Hydrogen Peroixde and water vapor.

Primary Advantages New 50 cm Pathlength G-SST Over The Previous 25 cm, 28.3 cm and the original 50 cm G-SST probe

  1. The double pass beam design (folded path) provides double of the beam interaction with the gases in the sterilizer chamber. This increases the achievable signal-to-noise making for a more accurate and stabile measurement. Since the absorbance of water and Hydrogen Peroxide vapor is very weak, this is a significant improvement in the measurement accuracy.
  2. The optics are sealed behind a window which isolates the lenses from the sterilization chamber; thus the probe is no longer sensitive to index of refraction changes, This makes the measurements are more stable under widely varying conditions of deep vacuum to high concentrations of water and hydrogen peroxide vapor.
  3. To allow the probe to be quickly serviced by a technician, the perforated cage around the beam path was to the open structure shown in Figure 2. With the lenses behind an o-ring sealed window, there is no adhesive degradation increasing the service life of the probe.

In addition to these engineering improvements, the newly designed G-SST probe is a form, fit, and function replacement for the older style G-SST probes. This allows for nearly effortless upgrading for existing customers who purchase the new and improved style of G-SST. The probe is available with a KF flange, sanitary flange, or flangeless. Obviously, the flanged probes are intended to insert into the sterilizer through a 2” [50 mm] flanged port thus the fiber optic cables remain outside of the chamber. However, all versions can be 100% immersed in the sterilizer chamber with the addition of 2 small o-rings.

Vapor Probe Features

  • Glass windows protect optical surfaces
  • High optical efficiency, > 50% transmission
  • Long pathlength, 50cm for greater accuracy and stability
  • Rugged design
  • SMA 905 fiber optic interface, all fiber sizes
  • Single-sided design, no need for fiber cable feed-throughs
  • Can be installed in vapor feed, return lines or sterilization chamber
  • Works in vacuum (10-5 Torr) or up to 2 atm absolute
  • Operates in an environment from 0°C to 90°C
  • P/N 19360-11050


  • 2 inch (50.8 mm) Tri-Clover port or 2 inch (50.8 mm) KF port
  • Electropolished 316 stainless steel or anodized aluminum body material
GSST Vapor Probe with Triclover fitting
GSST Vapor Probe with Triclover fitting

Probe Designed for Easy Servicing and Repairs

For hydrogen peroxide or other vapor applications, the 50cm G-SST Vapor Probe provides an efficient, simple and easy interface between the vapor chamber, and Guided Wave’s Hydrogen Peroxide Vapor (HPV) analyzers or other spectrometer or photometer. The probe clamps into a standard 2 inch Tri-Clover® sanitary fitting and can be mounted in the vapor chamber, feed line, or return line. Since both source and return fibers are on the same end of the probe, and external to the process, there are no fiber cables to seal. The optical path is folded, providing 50cm of interaction with the gas in a compact 25cm probe body. This means more accuracy and stability for low vapor concentrations.

Standard Probe Lengths 11.61in (29.49 cm), Insertion length 11.01 in (27.96 cm)
Pathlength 50 cm; double pass 25cm
Probe Diameter (inches) Flange 2.52 in, Probe Body 1.5 in, Insertion Body 1.74 in
Flange mount 2 in (50.8 mm) Tri-Clover or 2 in (50.8 mm) KF Flange Mount
Spectral Range NIR (600 - 2100 nm)
Optics Glass is gold-coated mirror
Fiber Diameter (μm)/Connector 200 μm – 600 μm; SMA 905
Efficiency ≥ 50% (900 nm – 1650 nm)
Temperature Range 0 °C to 90 °C
Pressure Range 1 x 10-5 Torr to 1520 Torr (2 atm)
Body Material SS316 standard, Electropolished or Anodized Aluminum
Window Material BK-7 glass
Seal Viton Sanitary Flange Gasket, Viton O-rings