Hydrogen Sulfide - Hazards, Releases & Precautions

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Chapter : Gas & Oil Safety

Gas Detection: Hydrogen Sulfide - Hazards, Releases & Precautions 

Hydrogen sulfide, or sour gas, is a flammable, colorless gas that is toxic at extremely low concentrations. It is heavier than air, and may accumulate in low-lying areas. It smells like "rotten eggs" at low concentrations and causes workers to quickly lose their sense of smell.

Many areas where the gas is found have been identified, but pockets of the gas can occur anywhere.
Iron sulfide is a byproduct of many oil and gas production operations and may spontaneously combust with air.
Flaring operations associated with hydrogen sulfide production will generate sulfur dioxide, another toxic gas.
Active monitoring for hydrogen sulfide gas and good planning and training programs for workers are the best ways to prevent injury and death. All personnel working in an area where concentrations of hydrogen sulfide may exceed the permissible exposure limit (PEL) (20 ppm for general industry and 10 ppm for construction) should be provided with training before beginning work assignments.

Releases

If a release of hydrogen sulfide in excess of the PEL is detected, OSHA recommends the following actions.
Implement a hydrogen sulfide contingency plan including, but not limited to:

• Appropriate instruction in the use of hydrogen sulfide safety equipment to all personnel present at all hydrogen sulfide hazard areas.
• Gas detection where hydrogen sulfide may exist.
• Appropriate respiratory protection for normal and emergency use must be followed as per organisation / As per country OSH Standards.
• For emergency response information, see Hazardous Waste and Emergency Response of organization / As per country OSH standard.

Hydrogen sulfide gas is very corrosive and therefore extremely hazardous. You need to take special precautions when choosing equipment and establishing safe work procedures.

All oil and gas well drilling sites should be classified according to areas of potential and or actual exposure to hydrogen sulfide. The recommendations and employee instruction will vary depending on the type of area:

• No Hazard Condition
• Low Hazard
• Medium Hazard
• High Hazard

No Hazard Condition

Any well that will not penetrate a known hydrogen sulfide formation would be categorized as a No Hazard Area. Special hydrogen sulfide–resistant equipment is not required.

Low Hazard

Work locations where atmospheric concentrations of hydrogen sulfide are less than 10ppm. Recommended for these areas:
• Hydrogen Sulfide warning sign with green flag warning device present.
• Keep all safety equipment in adequate working order.
• Store the equipment in accessible locations.

Medium Hazard

Work locations where atmospheric concentrations of hydrogen sulfide are greater than 10 ppm and less than 30 ppm. Recommended for these areas:

• Legible hydrogen sulfide warning sign with yellow flag warning device present.
• Keep a safe distance from dangerous locations if not working to decrease danger.
• Pay attention to audible and visual alarm systems.
• Follow the guidance of the operator representative.
• Keep all safety equipment in adequate working order.
• Store the equipment in accessible locations.
• An oxygen resuscitator.
• A properly calibrated, metered hydrogen sulfide detection instrument.

High Hazard

Work locations where atmospheric concentrations of hydrogen sulfide are greater than 30 ppm. Recommended for these areas:

• Post legible hydrogen sulfide warning sign with red flag warning device.
• Post signs 500 feet from the location on each road leading to the location, warning of the hydrogen sulfide hazard.
• Check all hydrogen sulfide safety equipment to ensure readiness before each tour change.
• Establish a means of communication or instruction for emergency procedures and maintain them on location, along with contact information of persons to be informed in case of emergencies.
• Ensure usability of two exits at each location.
• Do not permit employees on location without hydrogen sulfide safety training.
• Pay attention to audible and visual alarm systems.
• Store the equipment in accessible locations.

Two hydrogen sulfide detectors should be present (one should be a properly calibrated, metered detection instrument, and the other should be a pump type with detector tubes. Respiratory protection would be required if periodic testing indicates employee exposures to hydrogen sulfide at concentrations above the PEL.

• Oxygen resuscitator.
• Three wind socks and streamers.
• Two 30-minute- self-contained breathing apparatus for emergency escape from the contaminated area only.

Comprehensive training should be provided for workers in hydrogen sulfide operations. Example topics include:

• Identification of the characteristics, sources, and hazards of hydrogen sulfide.
• Proper use of the hydrogen sulfide detection methods used on the site.
• Recognition of, and proper response to, hydrogen sulfide warnings at the workplace.
• Proper rescue techniques and first-aid procedures to be used in a hydrogen sulfide exposure by personnel trained to recognize symptoms of exposure.
• Proper use and maintenance of personal protective equipment. Demonstrated proficiency in using PPE should be required.
• Worker awareness and understanding of workplace practices and maintenance procedures to protect personnel from exposure to hydrogen sulfide.
• Wind direction awareness and routes of egress.
• Confined space and enclosed facility entry procedures.
• Locations and use of safety equipment.
• Locations of safe briefing areas.
• Use and operation of hydrogen sulfide monitoring systems.
• Emergency response procedures, corrective action, and shutdown procedures.
• Effects of hydrogen sulfide on the components of the hydrogen sulfide handling system.
• The importance of drilling fluid treating plans prior to encountering hydrogen sulfide.