Hydrogen Sulfide: The Hidden Danger of Working Offshore
March 11, 2019 @ 8:00 pm
Updated on: March 5, 2021
Working on an offshore rig is always dangerous. When hydrogen sulfide (H2S) is present, offshore accidents become even riskier, and the simplest missteps can turn deadly. H2S is a potentially fatal threat that workers never see coming — yet it’s constantly present.
How Dangerous Is Hydrogen Sulfide in Offshore Accidents?
Hydrogen sulfide is a simple but deadly chemical compound—just two atoms of hydrogen and one atom of sulfur. Formally, it’s known as H2S, but other names include sour gas, rotten-egg gas, sewer gas and stink damp.
Crude petroleum, natural gas and mineral deposits are host environments for H2S. For the extraction industry, the toxic vapor is an ever-present threat because it’s both water- and oil-soluble, and agitation, heat or other processes can release it along with all its dangerous properties:
- It’s invisible, with no telltale discoloration or edge.
- It destroys a victim’s sense of smell. While the odor may initially seem strong, exposure paralyzes nerves in the nose, reducing the ability to smell H2S even though levels may be extremely high.
- It’s heavier than air, so it collects in low-lying, poorly ventilated areas.
- It’s highly reactive. H2S easily bonds to moisture, turning into sulfurous and sulfuric acids that are caustic and corrosive. H2S is also highly flammable. Fire yields sulfur dioxide, which is even more caustic than H2S and deadly at 20 parts per million. Associated iron sulfide scale is pyrophoric, prone to spontaneous ignition.
- It corrodes metal, concrete and other materials. Sulfurous acids cause problems like hydrogen embrittlement, sulfide stress cracking and crevice corrosion.
- It’s deadly even at low concentrations, capable of causing oxygen deprivation, respiratory paralysis, pulmonary edema and hemorrhaging.
Hydrogen Sulfide Safety Protocols
On an offshore rig, the potential for exposure to H2S exists for just about any area associated with drilling equipment or the drilling site, from the rig floor and substructures to the mud pump room or well testing equipment. Since H2S itself is not preventable, safety protocols for identifying risks and taking appropriate action are especially important.
To put into perspective just how important safety protocols are, the level of H2S gas deemed immediately dangerous to life and health—IDLH—is 100 parts per million (ppm). When a pipe corrodes from water condensation and H2S ruptures under pressure, for example, H2S concentrations may be as high as 40,000 ppm or more.
Even low levels of exposure can accumulate in sheltered areas, so workers need to be aware of the established limits for H2S. OSHA sets mandatory PEL-C (permissible exposure level ceiling concentration) at 20 ppm. The American Conference of Government Industrial Hygienists has set voluntary limits for H2S:
○ The TLV (threshold limit value) is 10 ppm for an eight-hour work day in a 40-hour week.
○ The STEL (short-term exposure level) is 15 ppm.
However, for longer shifts and long-term deployments, limits should be recalculated and reduced to provide for extended exposures.
Hydrogen Sulfide Safety Protocols
Employers are responsible for taking steps to reduce the risk of harm from hydrogen sulfide. Four key safety protocols are tailored to situations involving H2S. Each is important because if an oil company, their safety officers or foremen fail to follow each, workers can get hurt.
- Monitoring and Alert Systems: OSHA requires air testing for H2S concentrations, and that monitoring comes in both fixed and portable versions. Both types of systems monitor air continuously and can alert workers to concentrations that exceed set thresholds.
○ Fixed systems should have sensors positioned to ensure crew safety at all times, reliable power failure backups and a constantly manned control panel. Since many areas are noisy, alarms should have a visual component—like a strobe—as well as an audio alarm.
○ Portable or personal monitors are especially helpful in areas where workers may not be able to see or hear a fixed alarm. Portable units are also essential for emergency or rescue personnel. Complete calibration kits, battery chargers and sampling tubes are necessary to maintain them.
- Respiratory Protective Equipment: In an H2S environment, respiratory equipment must have positive pressure supplied air—equipment that pushes good air out of any leaks rather than allowing toxic gasses in. Three types of equipment may be used, depending on circumstances:
○ a self-contained breathing apparatus—SCBA;
○ a mask tied into a supplied air respirator—SAR—plus an auxiliary air cylinder; or
○ an escape mask pack, with a five-minute air cylinder.
- All workers should have training on and access to appropriate equipment that is properly maintained. Individuals entering IDLH scenarios must be equipped with SCBAs or SARs.
- Emergency Response and Rescues: Emergency protocols should include plans for onboard response crews, alarm systems, head counts, well shut-ins and leak resolutions, the clearing of H2S areas, stand-downs to resume operations, search and rescue operations, first aid and medical arrangements and evacuation and abandonment for critical situations.
- Training and Education: Outcomes depend on whether people have adequate training and practice. All workers who may be exposed must receive training and refresher courses. Curriculum should include the dangers that H2S presents as well as instruction on how to operate and maintain H2S detection systems and respiratory equipment. Training should educate workers on the limitations of their safety equipment, its proper care, what to do if it malfunctions, and the protocols established as part of the emergency response and rescue plans. Workers should also have ample opportunity to practice putting on, using and removing respiratory equipment.
Legal Options for Offshore H2S Injuries
Injuries from H2S offshore accidents vary widely because each is due to a particular level of toxic exposure over a certain time frame. Effects can develop over hours, days or months and intensify as prolonged exposures build.
If you’re dealing with the effects of hydrogen sulfide exposure and need assistance, reach out to the attorneys at Morrow, Morrow, Ryan, Bassett & Haik. Bring us your story, and we’ll listen. You can call 1-800-356-6776 or schedule your free consultation through our website.