13 Investigates Pemex facility chemical leak: Is hydrogen sulfide exposure putting you at risk?

DEER PARK, Texas (KTRK) -- When major leaks or fires happen at oil and gas facilities, complicated chemistry terms are often thrown around, but the main concern is simple: are you and your family safe?

One of the gases that leaked from the Pemex facility in Deer Park on Thursday was hydrogen sulfide.

ORIGINAL REPORT: 2 dead, at least 35 injured after chemical release reported at refinery in Deer Park, officials say

What are the crucial points you need to know if something like this happens again?

Hydrogen sulfide is often referred to as H2S.

Its nickname is "swamp gas," and if you smelled it in Pasadena or Deer Park, you know exactly why.

It's notorious for its "rotten egg" smell, but more importantly, the chemical is highly flammable and potentially lethal in high exposure.

Harris County Pollution Control monitors for the chemical because it is a byproduct of oil refining. You can see the results here: HCPCS Air Monitoring (arcgis.com), but the data from each testing site isn't easy to read unless you have a chemistry degree.

Ever since the county started checking H2S levels at these locations on Thursday around 6 p.m., their meters have been reading zero parts per million, which means no sign of any H2S.

UH Petroleum Engineering Professor Raman Krishnamoorti says if you ever see 300 parts per million, you are now in a dangerous situation.

700 parts per million can lead to unconsciousness and death, according to the Centers for Disease Control.

Professor Krishnamoorti believes if you smelled that rotting egg smell near Dear Park on Thursday, you probably experienced around 10 to 20 parts per million, which is low cause for concern.

"You will have a pretty strong smell of rotten eggs at about 20 parts per million," Professor Krishnamoorti said. "If they smelled it, it was still probably safe for them. They probably were exposed to it, but not at toxic levels. The problem with hydrogen sulfide is once a concentration goes up, you stop smelling it. And that becomes even more dangerous."

Professor Krishnamoorti says if you are sheltering in place, and you stop smelling that awful stench and begin to feel lethargic, you need to leave wherever you are and seek immediate medical care.

The Occupational Safety and Health Administration tells 13 Investigates it has not inspected the Pemex Deer Facility since it took it over from Shell, but the agency is investigating Thursday's fatal incident.

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