From 1987 to 1992, cadre at the Ministry of Defense.

From 1993 to 1997, he was director of operations of ERIC S.A. (risk management). Mr. Gérardin worked as  security consultant and engineer, safety/security auditor, and security risk management expert for companies and expatriates in Algeria during the crisis years. Management of fifty staff members.

In 1998 Mr. Gérardin founded GEOS, an international group that has shown strong growth over 10 years and is now recognized as the leading Risk Management and Business Intelligence firm in continental Europe. The Group had a turnover of 33,7 million euro in 2008, employs more than 400 experts and is present in over 80 countries. It provides companies and organizations with global operational assistance  for their protection and development.