Schematic drawing of the ASU process
An air separation unit (ASU) produces high-purity gases such as oxygen (O2), nitrogen (N2), and argon (Ar) via cryogenic distillation. These gases are used across industries including the steel, chemical, energy, electronics, and healthcare industries, where even trace impurities can impact processes.
HORIBA supports industrial and medical gas production with analyzers for continuous trace-level impurity monitoring down to ppb levels, as well as purity monitors covering the full 0–100% range. The portfolio also includes radiation thermometers for gas cylinder temperature monitoring.
HORIBA's Trace Gas Monitor GA-370 uses non-dispersive infrared (NDIR) photometry to measure trace levels of nitrous oxide (N2O) and carbon dioxide (CO2) behind the repurification unit. Trace levels of CO2 are also measured in the N2 and O2 product stream with a typical monitoring level of 1 ppm.
GA-370 Trace Gas Monitor
HORIBA's Sulfur Dioxide Monitor APSA-380 uses UV fluorescence to measure trace levels of total reduced sulfur (TRS) and sulfur dioxide (SO2) behind the repurification unit and in the N2 and O2 product stream.
APSA-380 Sulfur Dioxide Monitor
HORIBA's Hydrocarbon Monitor APHA-380 uses flame ionization detectors (FID) to measure trace levels of total hydrocarbons (THC) at the air inlet and behind the repurification unit.
APHA-380 Hydrocarbon Monitor
The GA-370 Trace Gas Monitor enables continuous, high-sensitivity monitoring of CO, CO2, CH4, and N2O in high-purity gases, supporting reliable quality control in air separation and semiconductor plants.
Download the brochure for detailed specifications and application insights.
Within the AP-380 Series, the APSA-380 is used for sulfur dioxide measurement and the APHA-380 for hydrocarbon measurement.
Download the brochures for detailed specifications and application information.
Trace Gas Monitor
Sulfur Dioxide Monitor
Hydrocarbon Monitor
Air Quality Monitor
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N2, O2, Ar: Air separator
CO2: Industrial sources or combustion
CO: Methane reformer (HyCO)
H2: H2O electrolysis and methane reformer
NH3: Haber-Bosch process
N2O: Heating of NH4NO3
NO: Oxidation of NH3
He: Natural gas sources
C2H4: Steam cracker
Non-dispersive infrared photometry (NDIR)
Used to measure impurities and purity levels in CO, CO2, N2O, CH4, etc.
UV fluorescence (after oxidation)
Used to measure impurities in SO2, H2S and other sulfur-containing compounds (TRS, TS).
Paramagnetic detector (PMD)
Used to measure impurities & purity in O2.
Chemiluminescence detector (CLD)
Used to measure impurities in NO, NO2, NOx.
Flame ionization detector (FID)
Used to measure impurities in CH4, C2H6, etc.
