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Prime Journal of Engineering and Technology Research (PJETR)

ISSN: 2315-5035

Volume 2, Issue 1, pp. 38-51

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Hydrogen sulphide concentrations a health risk to workers in geothermal power stations (A case study of Olkaria Geothermal Power Station in Kenya)



1Gikunju P, 1Njogu PM, and 2Makhonge PX



1Institute of Energy and Environmental Technology, JKUAT P .O. Box 62000-00200, Nairobi, Kenya
2Directorate of Occupational and Health, P. O. Box 34120-00100, Nairobi, Kenya

 Accepted Date

13th May, 2016



Gikunju P, Njogu PM, Makhonge PX (2016). Hydrogen sulphide concentrations a health risk to workers in geothermal power stations (A case study of Olkaria Geothermal Power Station in Kenya). Prim. J. Eng. Tech. Res. 2(1): 38-51.



Hydrogen sulphide (H2S) is a colourless gas identified with a strong odour of rotten eggs at low concentration. Due to its higher density than air tends to accumulate in low lying areas such as basements. Exposure to exogenous hydrogen sulphide is primarily by inhalation which is quickly absorbed through the lungs. Air quality monitoring in workplace is therefore an important exercise to establish indoor and outdoor exposure to toxic gases especially to comply with the World Health Organisation (WHO) and Occupational Safety and Health Standards in the work place and to monitor the ambient work environment to prevent adverse exposure. The goal of this study was to establish the ambient concentration of H2S at the Olkaria Geothermal Power Stations in Kenya and whether they pose health risk to the workers. H2S concentration was measured using a portable gas monitor at hourly intervals at predetermined locations. The data recorded was compared with the daily readings taken at the same locations in the past years of operation of the plants. The results indicates that there was presence of H2S in levels below the WHO Occupational exposure limits of 10ppm with Olkaria I and II recording an average concentration of 0.7 and 0.25ppm respectively and a range of zero to 1.8ppm and 3.2ppm respectively. The older plant has experienced higher mean of the daily peak readings of 0.49ppm from 1997 to 2011 and one time maximum reading of 6.4ppm at the stores and 6.0ppm at the seal pit. According the data analysis, there exist a risk of exposure in the areas where one minute readings of H2S above 5.4ppm have been recorded during a 12 hour shift. The research analysis shows where that the maximum readings and mean values have a positive correlation. Establishing a maximum reading would give an indication of the mean ambient condition with a correction factor of 1.845 and 1.839 for Olkaria II and Olkaria I. Therefore an average exposure of 3ppm would be indicated by a maximum exposure of 5.4ppm. 3ppm for 12hours is the equivalence of 10ppm for 8hrs based WHO TLV. The results indicated that the weak smell (0.1-1.0ppm) with offensive smell exist in greater than 80% of the non-zero readings incidences during the hourly and past daily measurements. Notable smell (1.0-2.0ppm) exist 14% and 8% in Olkaria I and II Geothermal power stations respectively. The concern is that prolonged exposure to H2S concentrations of 2-7ppm may cause nausea, tearing of the eyes, headaches or loss of sleep, and airway problems (bronchial constriction) in some asthma patients (Costigan, 2003). This study would recommend a review of settings warning system to correspond to lower than 10ppm for indoor workplaces where risk of exposure is apparent and occupancy is a 12hour shift.

Indoor, outdoor, pollution, geothermal, Olkaria, air quality


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Makhonge PX




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