Maine Security Officer Practice Exam 2024 - Free Security Officer Practice Questions and Study Guide

Fires require three main elements in order to start and continue to grow fuel, oxygen and heat. While helium and nitrogen are both gases that can contribute to a fire, they are not essential. Similarly, while carbon dioxide is produced in a fire, it is not one of the essential elements needed for a fire to start and grow. Therefore, the correct answer is option D - oxygen, heat and fuel.