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Compliance monitoring of hydrogen sulphide levels

The importance of compliance monitoring

Compliance monitoring is an important component of environmental management, ensuring that industry complies with global standards and guidelines. Umvoto has been undertaking compliance monitoring for various clients for a number of years, one of which is Tulu Moye Geothermal. In this instance, the quality of the air is measured and monitored to ensure that various gases don’t exceed World Health Organization human safety levels, which would directly impact on the surrounding communal settlements.

Tulu Moye Geothermal

Tulu Moye Geothermal (TMGO) is a joint venture between Meridiam and Reykjavik Geothermal, who are working in the south-eastern Ethiopian portion of the East African Rift Valley to generate renewable energy to supplement Ethiopia’s energy supply. The abstraction of this geothermal energy results in various gases being released from down-well fluids that require compliance monitoring for environmental and social health and safety. Typically, one of these gases is hydrogen sulphide (H2S) which causes the characteristic sulphurous odour associated with natural hot springs. At certain levels, this odour can be offensive and, at extreme concentrations, hazardous. The International Finance Corporation Environmental Health and Safety (IFC EHS) Guideline Limit for H2S detection, to which TMGO must comply, is 107 ppb per 24-hour average level (WHO, 2003). This is not for a point source (i.e., stack emission), but for environmental monitoring in the surrounding communal settlements. 

Series-400 Air Quality Sensors 

Umvoto and TMGO have selected the Series-400 Air Quality Sensors (AQTs) supplied by Vaisala (Finland).  These units are well priced and allow for the installation of several units covering a network of large tracts of communal occupied land surrounding the geothermal drill pad. Although the limited technology of these AQTs does not allow for accurate recording of the absolute H2S concentrations (the tendency is to overstate the actual value), they do provide indications of relative change and trends in the air chemistry thereby alerting the environmental monitoring team to take remedial action. To record absolute measurements for H2S would require a single point reference station; this would provide high accuracy but low density and at approximately 10 times the cost of the current network and would not satisfactorily cover the geographical range required in the recommendations of the Environmental and Social Impact Assessment. 

The recorded and interpreted air quality levels acknowledge that the actual environmental levels of H2S are below the mandatory thresholds. The air quality sensor network provides the most practical and cost-effective option as well as ensuring safe operating levels of H2S over the communal area of Tulu Moye. 

Contact us today if you’re needing compliance monitoring undertaken and we’ll assess the level of monitoring required!


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muizenberg, Cape town