Both NEBOSH and fire and safety course have good scope. NEBOSH Certificate-level qualifications give a good foundation in health and safety for managers, supervisors and staff with health and safety among their day to day responsibilities. There are many courses in fire and safety management----from certificate to PG Diploma. As you are a post graduate person you can do PG Diploma course. The eligibility for joining this course is any graduation.
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All these (marine , auto, industrial, oil and gas etc) have bright career prospects and you are the person to decide which one is best for your career.