Hydreka SA - A Halma Company , , Environmental XPRT Downloads About Solutions products industries services software training Publications videos articles Downloads Home Companies & Suppliers Hydreka SA - A Halma Company Downloads Hydreka Odalog L2 H2S Gas Recorder ... Hydreka Odalog L2 H2S Gas Recorder - Brochure Monitoring, control, survey rates H2S in sewer or a sewage works. Placeholder Placeholder Placeholder Placeholder Placeholder