Hydrogen Sulfide Special Precautions
All well drilling sites should be classified into areas of potential and/or actual exposure to hydrogen sulfide by the definitions outlined below. The safety recommendations made are a minimum. The American Petroleum Institute (API) has published "RP 49: Recommended Practice for Safe Drilling of Wells Containing Hydrogen Sulfide" which details recommendations in more depth and should be followed in all medium and high exposure areas. Below are OSHA and API definitions for each hazard area:
No Hazard Area - Any well that will not penetrate a known hydrogen sulfide formation. No special hydrogen sulfide equipment is needed (OSHA) (API).
API Condition I - Low Hazard Area - Work locations where atmospheric concentrations of H2S are less than 10ppm (OSHA). This includes any well that will penetrate a formation containing hydrogen sulfide that could result in atmospheric concentration of 10 ppm or less and/or in which the hydrogen sulfide zone has been effectively sealed off by casing/cementing and/or cementing method (API). For low-hazard areas, a 30-minute, self-contained breathing apparatus for emergency escape from the contaminated area only is recommended.
API Condition II - Medium Hazard Area - Work locations where atmospheric concentrations of H2S are greater than 10ppm and less than 30ppm (OSHA). Any well that will penetrate a formation containing hydrogen sulfide and is not defined as a low or no hazard area, including all exploratory (wildcat) well sites (API).
The following are recommended for medium hazard areas:
- NIOSH/MSHA approved manifold air masks with emergency escape cylinders for each employee
- two NIOSH/MSHA approved, 30-minute, self-contained breathing apparatus for emergency escape from the contaminated area only
- two wind socks and streamers
- oxygen resuscitator
- a properly calibrated, metered hydrogen sulfide detection instrument
- audible and visual alarm system
Knowledge Check Choose the best answer for the question.
7-7. Which of the following is designated as a work location where atmospheric concentrations of H2S are greater than 10ppm and less than 30ppm (OSHA).
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