| Period | Institution | Position |
|---|
| DEC 2014 - TO DATE | TECHNICAL UNIVERSITY OF KENYA | PROFESSOR |
| 2013 - TO DATE | SCHOOL OF GRADUATE AND ADVANCED STUDIES, TECHNICAL UNIVERSITY OF KENYA | DIRECTOR |
| FEB 2000 - FEB 2002 | INSITUTE OF ECOLOGICAL CHEMISRTY, GERMAN NATIONAL RESEARCH CENTRE FOR ENVIRONMENT, MUNICH | HUMBOLDT RESEARCH FELLOW |
| DEC 1988 - FEB 1995 | KENYA INDUSTRIAL RESEARCH AND DEVELOPMENT INSTITUTE. | RESEARCH OFFICER |
| AUG 1983 - DEC 1988 | MINISTRY OF ENERGY | CHEMIST |
| JAN 2002 - AUGST 2004 | CENTRE FOR ECOLOGY AND HYDROLOGY, UK | POSTDOCTORAL RESEARCH FELLOW |
| 2006 - APRIL 2010 | MASENO UNIVERSITY | SENIOR LECTURER |
| 2010 - 2014 | TECHNICAL UNIVERSITY OF KENYA | ASSOCIATE PROFESSOR |
| APRIL 2011 - 2013 | TECHNICAL UNIVERSITY OF KENYA | DIRECTOR OF RESEARCH AND POSTGRADUATE PROGRAMMES |
| February 1995 - 2006 | MASENO UNIVERSITY | LECTURER |
