VPE Korea installed monitors for a wastewater stripper tank / filter tank confined space. Even when oxygen reads 20.9%, H₂S can remain dangerous—always double-check sulfide alongside O₂. Technical support: 02-2088-7334.

Pre-entry verification—operators smelled H₂S immediately upon opening the hatch.

After ventilation, oxygen stayed flat but H₂S remained between ~5 and 15 ppm—proof the hazard was not solved by air movement alone.

FIX800 installation—LED board above the entrance shows “do not enter” messaging during alarm.

LED messaging—intuitive icons communicate risk faster than numeric tables alone.

Even with exhaust fans, H₂S rebounded above 20 ppm after doors closed—other sites show stable oxygen yet high sulfide; never rely on a single channel.