LAUSR

Trondheim municipality uses four-gas alarm equipment as part of their personal protective equipment (PPE) in wastewater related work. Approximately 65 sensors are personal, and 60 of them are included in the study. 15 second recordings and alarm data for hydrogen sulphide (H2S), oxygen (O2), lower explosive limit (LEL) and carbon monoxide (CO) from more than 7000 workdays are presented. We have mainly studied H2S, but here we present data and correlation from all four sensors in the equipment. The sensor setup has been chosen to cover the most common gas exposure of the occupation: H2S and LEL (calibrated as methane, CH4) caused by biological degradation, CO from machinery and O2 deprivation, mainly thought to be caused by use (corrosion or burning) and/ or by displacement by other gases. Many workers still think use of a single sensor gas detector is enough for protection against all gases. An algorithm that makes this calculation from measurement data is published. The algorithm was adapted to data export format from logging gas alarm equipment MicroClipX3 from Honeywell Analytics. Data from more than 7000 workdays in sewage related work was collected. There were no obvious correlations between the measured gas concentrations. All four gases are relevant to measure in wastewater related work. None of them can substitute each other.