At higher concentrations H2S can
deaden your sense of smell.
Hydrogen Sulfide is an extremely
toxic gas that is colorless,
flammable, heavier than air,
soluble in water, and has the
smell of rotten eggs at lower
How Is Hydrogen Sulfide Formed?
• Dark damp places where bacteria is present.
Hydrogen Sulfide is generated as a
common by-product of industrial and
Hydrogen Sulfide is formed under low oxygen conditions
when sufficient amounts of sulfur and bacteria are
present. H2S can be formed in many places such as:
• Oil and gas reservoirs.
• Sewers and sewage processing facilities.
H2S is a by-product formed when
organic matter decays.
Where Is Hydrogen Sulfide Found?
Hydrogen Sulfide can be found
almost anywhere that oil,
water, and gas are produced.
Pits, Cellars or Sewers.
Sulfur Removal Systems
Vapor Recovery Units
Wellheads or Tanks
What are the Health Hazards of H2S?
H2S will enter through the lungs and is
considered a chemical asphyxiate.
Hydrogen Sulfide can have an array of
health effects on the body depending
on exposure concentrations.
It blocks the transfer of oxygen to the blood
cells and causes paralysis of the respiratory
Immediately Dangerous to Life or Health: 100 ppm
Here are the Hydrogen Sulfide (H2S)
Permissible Exposure Limit: 10 ppm for an 8-hr period avg.
Short Term Exposure Limit: 15 ppm for a 15-minute avg.
Concentration Levels & Effects
The following table below lists the health effects of
exposure to H2S.
Concentration Health Effects
10 ppm Beginning eye irritation
50-100 ppm Slight respiratory tract irritation after 1 hour exposure.
100 ppm Coughing, eye irritation, loss of sense of smell after 2-15 minutes. Altered
respiration, pain in the eyes, and drowsiness after 15-30 minutes followed by
throat irritation after 1 hour. Several hours exposure results in gradual
increase in severity of these symptoms and death may occur within the next
200-300 ppm Severe respiratory tract irritation after 1 hour of exposure. Possible
pulmonary edema (fluid in the lungs).
500-700 ppm Loss of consciousness and possibly death in 30 minutes to 1 hour.
700-1,000 ppm Rapid unconsciousness, loss of respiration, and death after 1-3 minutes.
1,000-2,000ppm Unconsciousness at once, loss of respiration and death in a few minutes.
Death may occur even if individual is removed to fresh air at once.
A variety of equipment can be used to do this:
As mentioned, one of Hydrogen Sulfide's effects on the
body is it deadens the sense of smell at fairly low
This can cause a false sense of security
and therefore we must use air monitoring
equipment to detect H2S.
Portable monitors that can be hand held or attached to
Fixed monitors can be located where contamination is
Alarms to alert personnel when H2S levels exceed
permissible exposure limits.
When Do We Monitor?
Examples of when air monitoring shall be performed
Air monitoring should be done anytime there is a potential
for someone to be exposed over the PEL of H2S.
• Any time there is a potential to be exposed over the PEL.
• At all times when working around H2S concentrations
• During all confined space entries.
• When gauging tanks.
• Never go directly upwind (you may be running into the
Should a release occur here are some escape guidelines
you must follow.
• Know the alarm systems.
• Know where the potential sources for H2S are located.
• Know the wind direction at all times.
• Escape by getting upwind to a higher elevation (if
possible) from the source.
• When escaping, always go cross wind and around the
Take H2S seriously… follow all safe guidelines and
standards. Remember; always ask a supervisor if unsure
Hydrogen Sulfide is deadly, especially when you don’t
understand or respect its dangers.
It’s a matter of life or death.
Short exposure to 100ppm hydrogen sulfide will cause
Hydrogen sulfide is invisible, flammable, explosive and
When a hydrogen sulfide emergency occurs, rescue any
victims first, then protect yourself.
Hydrogen sulfide is heavier than air, so it collects in low-
You do not need to worry about H2S unless you detect a
Emergency escape units can be used to enter and work in
To avoid exposure to H2S, you should remain “wind
Your breathing apparatus should always be positive-
pressure, never air-purifying.
After you’ve been trained to use respiratory protection,
you won’t have to worry about additional training.
If you suspect H2S is present in your work area, you
should move immediately downwind away from the area.