• Carry out a desk study to identify ground gas sources before work starts.
• Monitor for methane, CO2, O2, and H2S as a minimum at all excavations.
• Calibrate gas detection instruments to the manufacturer's schedule.
• Record all monitoring results and compare against trigger and action levels.
• Ventilate excavations and enclosed spaces before and during work.
• Ensure all operatives know alarm thresholds and the evacuation procedure.
• Use intrinsically safe equipment where flammable gases may be present.
• Re-monitor after breaks, shift changes, or any change in conditions.
• Include ground gas risk in the site-specific risk assessment.
• Report any unexpected odours, readings, or symptoms immediately.

• DON'T enter any excavation without checking the atmosphere first.
• DON'T rely on smell to detect gases — some are odourless or deaden senses.
• DON'T use uncalibrated or out-of-date gas detection equipment.
• DON'T ignore low-level readings — they can increase rapidly.
• DON'T smoke, use naked flames, or create sparks near gas risk areas.
• DON'T assume gas levels are safe because they were clear earlier today.
• DON'T work in oxygen-depleted atmospheres without breathing apparatus and rescue.
• DON'T store monitoring equipment near contaminants affecting sensor accuracy.
• DON'T dismiss headaches or dizziness — these may indicate gas exposure.
• DON'T skip monitoring because the site looks or smells normal.

See also: Contaminated Land Safety Awareness | Atmospheric Monitoring and Gas Testing