Toxic Gas in Oil and Gas Drilling

Hydrogen Sulfide gas can be one of the most vicious and deadly hazards in the oil and gas industry. It goes by many names such as H2S, sour gas and sulfureted hydrogen, and workers in the oil and gas industry are very aware of its lethal properties. Found in formations that are being drilled for oil, the gas is formed by decomposition of organic matter containing sulfur.

Hydrogen sulfide is a highly toxic, colorless, combustible gas. It is heavier than air and has the unmistakable odor of rotten eggs. However the sense of smell is not a reliable warning because exposure to this gas quickly deadens the sense of smell; relying on being able to detect its odor can provide a false sense of security.

Loss of consciousness can occur within seconds of exposure to a high concentration of this gas. The only positive means of determining the amount of H2S present is by testing with approved detectors. If H2S is suspected, the concentration must be determined before personnel are allowed in the area. If it is found to be present, the following procedures should be adopted:

The drilling rig must be equipped with fixed electronic H2S monitors, along with audible and visual alarms.
Calibration must be performed according to manufacturer's instructions which in most cases is daily.
At least two wind direction indicators must be installed in locations visible from the rig floor, shale shakers, and mud tanks.
At least one blower must be located on the rig floor; but blowers are also highly recommended at the shale shaker, mud tank and cellar floor.
H2S warning signs must be located no more than ¼ mile from the well.
At least two designated safe briefing areas with at least two sets of self-contained breathing apparatus (SCBA's) must be located in each area.
Emergency escape breathing units must be kept on the rig floor, monkey board, shale shaker and mud tank.
All personnel working on location must have completed an approved H2S training program.
Extra caution must be used around low places such as cellars, ditches, etc., since H2S is heavier than air and tends to collect in these areas--especially if there are no blowers in place.
In areas where high concentrations are likely, employees should work in pairs, with breathing units readily available.
All personnel must avoid entering any confined space, such as a tank, vessel, or other enclosed area unless (1) they have received confined space entry training, (2) they have a permit for entry when required, and (3) the space has been tested and found safe for entry.