Equally important to examining the worksite environment for potential areas of risk is understanding the health-related issues associated with H2S exposure. Similar to most gases, the level of impact to a worker’s health directly corresponds to the concentration of exposure in parts per million (ppm) and duration of exposure. For example:

  • .13 ppm: The threshold of odor detection.
  • 10-100 ppm: Eye and throat irritationand headaches can occur after one hour of exposure. A worker may experience nausea, dizziness, coughing and vomiting due to continued exposure.
  • 700-1000 ppm: This amount of H2S can cause unconsciousness and immediate collapse within one or two breaths. Continued exposure at this amount may be fatal.
  • 1000-2000 ppm: Nearly instant death occurs when exposed to this amount of H2S.
  • 45,000 and 450,000 ppm: An explosion can occur at this level of exposure.

After identifying the degree of severity of a potential H2S event, the respirator selection process will then depend on the standards and guidelines of each country. For example, worksites in the United States will follow the OSHA respiratory selection regulations, which are determined by the maximum use concentration (MUC). This figure is the multiplication of the assigned protection factor (APF) and the recommended exposure limit (REL). OSHA’s standard 29 CFR 1910.134 will detail the APF of a certain class of respirators and NIOSH’s Pocket guide to Chemical Hazards shows exposure limits.

The following respirator types are suggested based on their corresponding concentrations of H2S:

  • 0-10 ppm: No respirator is needed, below REL.
  • 10-100 ppm: Powered air-purifying respirator (PAPR), full face mask cartridge respirator or self-contained breathing apparatuses (SCBA).
  • 100-100,000 ppm: SCBA or supplied air in positive pressure mode.

Companies shouldn’t rule out the possibility that there may be circumstances where workers could be exposed to H2S concentrations exceeding 100,000 ppm, including drilling operations or work-overs of low-producing wells. If the initial assessment identifies this scenario as a potential threat, companies can refer to the manufacturer’s simulated workplace protection factor (SWPF) test. Some manufacturers have tested their respirators with sulfur hexafluoride (SF6) to replicate the safety challenges that arise during H2S exposure, finding that some SBCAs provide protection above industry standards. In these tests, 3D head scans are created, which are then used to help devise exercises that simulate escape situations, helping prepare workers for the unexpected.

Across these high-risk industries, companies can demonstrate their commitment to the safety of their workforce by proactively and intelligently identifying hazardous situations. This process is critical to the success of these businesses. It is essential that managers pledge to reduce the number of work-related respiratory injuries and invest in quality respirators to combat extreme environments.