Hazardous Characteristics Copy

Hazardous Characteristics

If You take the chance … and Reject the Training, Safe work practices, and Safeguards that are in place.
Then Prepare, for the Fate that Follows !!

Auto Ignition Temperature

Hydrogen Sulfide will automatically ignite at 500 0F

End of lit cigarette – 1400 0F

Diesel exhaust – 600-2400 0F

How do we control this toxic gas?

  1. Engineering Controls
    1. —Ventilation
      1. —Natural
      2. —Manufactured
    2. —Flare Stack
    3. —Venting
  2. —PPE
    1. —Supplied Air Respirator
      1. —SCBA
      2. —Work line
      3. —Escape Pack

Supplied Air Sources

Self Contained Breathing Apparatus (SCBA)

Air Trailer – Work-line


  1. All breathing apparatus contain Class D breathing air; not oxygen!
  2. ELSA Escape Air Pack – Usually 5 minutes air for escape only.
  3. Work-line unit – Attached to large bottles of breathing air or a compressor with hoses.  Also contains a 5 minute bottle of air worn by worker to be used for moving to another work-line or escape from contaminated area.
  4. Self Contained Breathing Apparatus (SCBA) – used to work in contaminated area, rescue of downed worker, or escape from contaminated area.
  5. Only positive pressure regulators are allowed in H2S environments.  This means the air flows constantly from the regulator to the face-piece keeping a constant pressure inside the face-piece.


  1. Facial hair – Facial hair between the sealing surface of the respirator face-piece and the wearer’s skin may prevent an effective seal.
  2. Contact lenses – May be worn with full face respirator.
  3. Corrective spectacles – Should not be worn if equipped with temple bars or straps that interfere with the respirator face seal.
  4. Psychological issues – such as claustrophobia are a definite hazard to the wearer of a respirator.
  5. Facial disfigurements – such as scars, false teeth, bad acne, broken jaws, etc.

What else can we do?

  1. Tail gate meetings
  2. Education
  3. Buddy System
  4. Be Wind Aware
  5. Eliminate Ignition Sources
  6. Keep non-essential personnel out of area
  7. Checking Safety Equipment

By-products of Burning

When H2S is burned, it produces Sulfur Dioxide

  1. Short-term exposures to high levels of sulfur dioxide can be life-threatening.
  2. Exposure to 100 ppm of sulfur dioxide is considered immediately dangerous to life and health (IDLH)
  3. PEL for SO2 is 2 ppm
  4. Sulfur Dioxide may cause heart problems and respiratory disorders in younger children and elders.

Flare stack

If the flare stack is burning away 100,000ppm H2S and is burning at 80% efficiency, what is the ppm of H2S in the exhaust plume?

100,000ppm. The flare stack is burning 80% of the volume not the concentration.

H2S reacts with iron and steel which forms iron sulfide which can be Pyrophoric !

Iron Sulfide in pipes and tanks which will spontaneously ignite upon contact with air.

Iron sulfide treated with acids results in H2S being released.


H2S dissolves in water to form a weak acid that corrodes and pits metals.


H2S may react with iron and steel causing hydrogen embrittlement and/or sulfide stress cracking. This lowers safety factors in tubular and pressure vessels.

Hazardous Characteristics


H2S is the second most toxic gas known to man.

The most toxic is Hydrogen Cyanide

PEL of H2S   =  10 ppm
PEL of HCN =  10 ppm

Target Organs

Signs of H2S Exposure

Eye irritation

Respiratory irritation
Pulmonary edema


  1. When a person breathes H2S gas it goes directly through the lungs and into the bloodstream.
  2. To protect itself, the body oxidizes the H2S as rapidly as possible into a harmless compound.
  3. If so much gas is breathed that the body cannot oxidize all of it, the H2S builds up in the blood and poisons the individual.
  4. The nerve center in the brain which controls breathing is paralyzed, the lungs stop working & the person is asphyxiated

Variables that determine the effects of H2S exposure

  1. Time (how long)
  2. Concentration (how much)
  3. Frequency (how often)
  4. Variables associated with the individual.

Individual Variables

What is a Part Per Million (ppm)?

One part in a Million Parts.

1 inch in 15.5 miles.


1 ounce in 31.25 tons

1 second in 11.5 days

1 drop of  Vodka in 80 fifths of 7-up.


  1. 0.13 ppm Can first smell the gas
  2. 4.6 ppm Moderate rotten egg odor
  3. 10 ppm Beginning of eye irritation(PEL)
  4. 27 ppm Strong rotten egg odor
  5. 100 ppm Coughing, eye irritation, loss of sense of smell, Buddy system required, Immediately Dangerous to Life & Health (IDLH)
  6. 200-300 ppm -Eye irritation, respiratory tract irritation after one hour.
  7. 500-700 ppm –Loss of consciousness & possible death in 30 minutes to 1 hour.
  8. 700-1000 –Rapid unconsciousness at once, cessation of respiration & death
  9. 1000-2000 –Unconsciousness at once, early cessation of respiration & death in 3 minutes or less. Death may occur even if rescued.

Exposure Levels

PEL – 10 ppm / 8hr. TWA
PEL – 6.6 ppm / 12hr. TWA
PEL – 5 ppm / 16hr. TWA
STEL – 15 ppm / 15 min.

Ceiling Concentration – 50 ppm / once 10 min.
Human Lethal Concentration
100 – 800 ppm / 5min.
Revised IDLH – 100 ppm