Home Podcasts THMG059 – Hydrogen Sulfide, Part I

THMG059 – Hydrogen Sulfide, Part I


In this episode, we begin to explore one of the most common chemicals we respond to: hydrogen sulfide.

Complete Show Notes

2:45 Overview of Hydrogen Sulfide

  • Extremely common substance that’s also flammable, corrosive, poisonous, and toxic
  • Poisons have a noxious effect on a living organism, while toxins are poisons produced by living organisms
  • Also known as acid, sewer gas, sour gas, sulfur hydride, dye, stink damp, etc.
  • Hydrogen sulfide (H2S) is a naturally occurring product that commonly results from the breakdown of organic matter (plants, animals, etc.) and waste
  • Created when bacteria and fungi eat the organic matter that contains sulfur and the amino acids it contains – sulfur is then metabolized and released as hydrogen sulfide
  • Since we’re dealing with a gas that tends to accumulate in low-lying and low-ventilation areas, it’s likely to come back up through waste systems
  • These areas include manholes, wells, basements, bunkers, etc.
  • The oil and gas industries are both very familiar with this chemical
  • Hydrogen sulfide is frequently the cause of death in areas where there’s a lot of drilling
  • Also used frequently in suicide since there’s a pretty good success rate

9:10 Chemical-Physical Properties of Hydrogen Sulfide

  • Very low concentration, which means it’s always just floating around in the air
  • Odor becomes more offensive at 3-5 PPM – this is where our sensitivities come into play and we pick up on the presence of hydrogen sulfide
  • Above 30 PPM, the odor is described as sickeningly sweet and almost overwhelms the senses
  • At 2-5 PPM, any prolonged exposure causes nausea, tearing at the eyes, headaches, loss of sleep, and airway problems
  • At 20 PPM, there’s a possibility for fatigue, loss of appetite, headache, irritability, poor memory, and dizziness
  • At 50-100 PPM, there’s slight conjunctivitis, respiratory tract irritation, digestive upset and loss of appetite
  • At 100 PPM, symptoms include coughing, eye irritation, olfactory fatigue, altered breathing, drowsiness (after 15-30 minutes), and throat irritation (after 1 hour) – all of these side effects increase the longer you’re exposed, and death can occur within 48 hours
  • At 100-150 PPM, you’ll lose your sense of smell
  • At 200-300 PPM, there’s marked conjunctivitis and respiratory tract irritation within 1 hour – pulmonary edema may occur from prolonged exposure at this rate
  • At 500-700 PPM, there’s staggering, collapse (within 5 minutes), serious damage to the eyes (after 30 minutes), and death after 30-60 minutes of exposure
  • At 700-1,000 PPM, you’re knocked unconscious almost immediately – death occurs within minutes if you don’t escape the cloud
  • At 1,000-2,000 PPM, death is nearly instantaneous
  • Olfactory fatigue
    • The concentration is so high that your brain stops processing olfactory signals – this makes people think they’re away from the contaminant, which is very dangerous because they probably aren’t
    • You have to depend on your meter since you’ve lost your sense of smell – incredibly important when dealing with hydrogen sulfide

13:35 How Hydrogen Sulfide Affects Your Body

  • Most common route of entry into the body for hydrogen sulfide is inhalation
  • Once it’s entered the lungs, it gets into the circulatory system – at this point, you’re dead
  • Hydrogen sulfide gets to the very depths of the cells – affects the mitochondria, which is where all of our energy (ATP) comes from
  • H2S is fat soluble, so it moves right through our membranes – turns off your lungs from the brain stem like a light switch if there’s enough PPM
  • Hydrogen sulfide can have lasting effects on your body, even if you’re only exposed to a small concentration
  • It can mess with your breathing, cause heart attacks, and lead to a condition called neuropsychiatric sequelae

15:05 Flammability and Detection

  • Quite a wide range of flammability – LEL is 4.5 and UEL is 45.5 – most other gasses don’t have this kind of range
  • We like narrow ranges in hazmat, so hydrogen sulfide is very worrisome and difficult to deal with
  • Don’t follow your nose – instead, use your meters
  • Acetate paper
    • Changes color from white to brown in the presence of hydrogen sulfide – there’s a direct relation between PPM and the quickness of the color change
    • There’s no notification system with this method, so you have to remember to look at your paper
  • Colorimetric tubes and chips
    • Give us a very accurate reading of the amount of hydrogen sulfide in the atmosphere – air is pulled through tubes and meter gives you a clear color change
    • These are a little clumsy, and you have to pump them to get them to work
  • Electrically-controlled detectors
    • Metal oxide – very sensitive to combustible gasses at a low PPM
    • Electrochemical sensor – tells us the LEL, measures at the PPM range, and can be alarmed
    • GCMS and NDIR – these can also help us pick up on hydrogen sulfide
    • PID – these have an IP of 10.46, so they can also pick up H2S
    • FID (flame ionization detectors) will not measure hydrogen sulfide because it can only measure organic substances

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