The Invisible Killer – How to Prevent H2S Exposure at Wellsites


There are many potential dangers at wellsites. One of the most insidious is accidental inhalation of toxic gas. Hydrogen Sulfide—also known as H2S, sewer gas, swamp gas, stink damp, and sour damp—is a colorless gas known for its pungent “rotten egg” odor at low concentrations. Any wellsite H2S has the possibility of having H2S present. The Southwestern United States has recorded the most prevalent concentrations. Particularly sites in New Mexico, Texas, Louisiana, and Oklahoma. H2S is extremely flammable and highly toxic.

According to the Bureau of Labor Statistics, H2S caused 60 worker deaths between 2001 and 2010. Another study by the U.S. National Library of Medicine reported that 52 workers died of hydrogen sulfide toxicity between 1993 and 1999. Workers in their first year of employment with the company are most common in the reported deaths. In 21% of cases, a co-worker died simultaneously or in the attempt to save the workers.

Needless to say, it is important to understand how to identify the presence of toxic gas.

However, this matter has recently gotten trickier, especially in shale plays. Customers have informed us that in some cases H2S may not be present at a site during initial production, as many 6-8 months long, and then overnight deadly levels come to the surface.

To cover this risk and protect themselves, some operators are now putting up windsocks, orange flags, and signs that state: “H2S may be present.” This is understandable, but clarity on this issue is critical. Here are a few things to be aware of on site:

  1. Orange windsocks only signify wind direction.Wind direction is important to be able to determine the muster point in case of an accident. Muster points should always becrosswind or slightly upwind, away from possible exposure to bad gasses, flames, or liquid releases that can be toxic or damaging to equipment.
  2. Watch the legend at the entrance. While orange windsocks or flags do not indicate that H2S is present, if you see them you need to be on alert. There should be a red, yellow, or green flag at the site entrance where H2S has been detected.  There should also be a legend to tell you what those flags indicate with it.
  3. Use a personal monitor. A personal gas monitor may save your life, so carry this with you anytime you visit a site and make sure it is switched on. If the alarm sounds, get out of that location.

Stay aware and stay alive.