Hydrogen Sulfide (H₂S) is a highly toxic and flammable gas commonly encountered in oil and gas drilling—especially in sour fields like those in parts of Iraq and Kurdistan.
Colorless but has a rotten egg smell at low concentrations.
Heavier than air, so it tends to accumulate in low-lying areas.
Exposure at even low ppm levels is hazardous; concentrations over 100 ppm can be immediately life-threatening.

Normal Response to H2S Detection
Standard protocol when H₂S is detected includes:
Immediate alarm activation.
Personnel evacuation or donning of SCBA.
Shutting down non-essential operations.
Initiating Emergency Response Plans (ERP).

Why Might Drilling Continue With SCBA Use?
There are certain controlled conditions where continuing operations may be necessary:
Well Control Priority: If stopping operations could lead to a blowout or worsen the situation, continuing with PPE is safer than abandoning the operation.
Specialized Crew: Only trained personnel equipped with SCBAs may be allowed to proceed with critical actions.
Ventilation and Monitoring: Continuous gas monitoring, and H₂S dispersion systems are in place.
Zone Classification: Sometimes the area is partially safe (e.g., open-air rigs), and the gas is localized.

Use of SCBAs During H2S Events
SCBA gear is a last line of defense in high-risk zones. Key points:
Provides clean air from a compressed tank, not ambient air.
Personnel are trained in emergency breathing apparatus (EBA) use.
Worn during:
H₂S alarms.
Work in known sour zones.
Emergency well control actions.

Personnel appear to continue work while fully geared with SCBAs.
This indicates a controlled environment with:
Real-time gas monitoring.
Likely trained response to a non-critical H₂S release.
Emphasis on maintaining well control without escalating the risk.