Working in oil & Gas and Petrochemicals means handling large quantities of flammable, toxic materials and entering hazardous areas, so the potential for serious accidents is clear. Chapter 1: Introduction, which includes safety questionnaire and analysis of safety regulations in different countries. Chapter 2: Safe Work Procedure; explains the permit to work system and the responsibilities for each side in the work permit, communication, work coordination, hazard assessment and job safety analysis. Chapter 3: Electrical Installations in Hazardous Areas; describes the principles of explosion protection, explains and compares between the National Electrical Code (NEC) and International Electro-technical Commission (IEC) Area Classification, and helps in selecting appropriate equipment suitable for use in Potentially Explosive Atmospheres. Chapter 4: Chemical Reactivity Hazards; explains the Physical Hazards and Health Hazards of chemical substances, and the appropriate way of chemicals handling. Chapter 5: Functional Safety, Review the new functional safety regulations according to the international standards IEC 61508 and IEC 61511, which has been modified to apply functional safety concept for all control equipment.