What must be done before entering any underground or surface with potential explosive gas?

• A. Put on a bright colored hard hat
• B. Rely on sight only to judge safety
• C. Begin work and monitor gas later
• D. Ensure ventilation and gas monitoring are in place; verify detectors function; obtain clearance

Answer: (D)

Before entering any area with potential explosive gas, make sure the atmosphere is controlled and monitored. Ventilation must be in place to dilute and remove hazardous gases, creating a safe breathing environment. Gas monitoring should be active to provide real-time readings of gas concentrations and oxygen levels, giving early warning if conditions become unsafe. Detectors and alarm systems must be tested and proven to function correctly so you can rely on them, not just guess or wait for symptoms. Finally, obtain proper clearance from a supervisor or responsible authority, confirming that the area meets safety limits and that entry is authorized and planned, with monitoring ongoing. Without these steps, you could be exposed to an explosive atmosphere at any time.