Hydrogen Sulphide | Safety
What is H2S?
Hydrogen Sulfide is a highly poisonous, invisible & explosive gas that is heavier than air. Its formula is H2S. Hydrogen sulfide has a distinctive smell of rotten eggs & at higher concentrations, it quickly deadens the sense of smell. Therefore you cannot trust your nose when dealing with H2S.
H2S is referred to:
- H2S
- Sour Gas
- Rotten Egg Gas
- Silent Killer
Where do you find H2S?
The gas is the product of the Bacterial degradation of organic animal or vegetable matter and is not confined to any specific location. It can be found wherever organic decomposition has occurred & is a serious hazard to the health of workers in Oil & Gas drilling operations & refineries, industrial sites, farms, sewage workers, fishing industry, etc.
Properties of H2S
Hydrogen Sulfide Gas has the following characteristics:
- Extremely Toxic.
- Colorless.
- Odour of rotten eggs in low concentrations only.
- Heavier than air.
- Readily dispersed by wind movement or air currents.
- Highly flammable (forms an explosive mixture with air between 4.3% to 46% by volume concentration).
- Burns with a blue flame to produce Sulphur Dioxide (SO2), another toxic gas.
- Soluble in water.
- Highly corrosive to certain metals.
Health Hazards of H2S
The effects of H2S is directly proportional to exposure time and level of H2S exposed. At a lower level of exposure may cause the following symptoms individually or in combinations:
- Headache
- Coughing
- Drowsiness
- Dizziness
- Irritated skin
- Loss of appetite
- Fatigue
- Nausea
- Dryness of throat
- Sensations of pain in the nose
- Chest Pain
Moderate Level of exposure may cause the following symptoms individually or in combinations:
Severe irritation to nose and eyes
- Headache
- Dizziness
- Nausea
- Coughing
- Vomiting
- Difficulty in breathing
High level of exposure may cause the following symptoms individually or in combinations:
- Shock
- Convulsions
- Unable to breath
- Coma
- Death
- Degree of Physical effect
Degree of physical effect of exposure depends on four factors:
- Duration of Exposure.
- Level of Concentration.
- The physical condition of the person.
- Frequency of exposure (resistance is lowered by repeated exposures)
The consumption of alcohol during the 24 hours prior to exposure to H2S will make you more susceptible to the adverse reactions at lower levels of concentration.
Detection techniques of H2S
There are three different types of monitors for detecting Hydrogen Sulfide:
- Fixed Monitor System.
- Personal Portable H2S Monitor.
- Personal Detector.
Fixed Monitor System
H2S gas contacts an electronic sensor. The sensor sends an electronic signal to the main control panel which is a combination computer/calculator/display panel. The electronic signal is calculated and computed as a measure of the concentration of H2S in parts per millions (ppm). This measurement is displayed on a meter on the controller. The controller gives off a signal to let you know the gas has been detected & that you need to look at the panel. At the same time, it sends an electrical signal to warning lights & sirens set up at various places, giving a general alarm that there is a dangerous situation & that gas is in the air around the sensor.
If such a system has been installed at your place of work, be sure you know where all the sensors are placed & notify your supervisor if you see that any of them have been damaged.
Personal Electronic Monitor
The units are usually hand-held or belt-mounted & measure the H2S concentration at the sensor head continuously. Monitors give an audible alarm, some readout, at a pre-set level of H2S. They should be worn as low as possible, definitely not higher than the waist.
Some advantages of this type of detector are:
- Portable & lightweight.
- Detects H2S within 30 seconds.
- Adjustable audible H2S alarm points.
- No loss of sensitivity due to a lack of exposure to H2S.
- Will not be poisoned by overexposure to H2S.
- Battery-operated.
Personal Detector
The following are some common detection devices:
- Lead acetate tape
- Ampoules
- coated strips
These change color (usually turn brown or black) in the presence of H2S. The color change indicates the concentration of H2S. This is suitable for use in a low concentration of gas only. They should be used as an alternate method of detection.
Hand-Operated Tube Detectors
This type of detector incorporates a pump, colorimetric detector tube & a scale that gives a reading of H2S. The pump pushed air tested through the detector tube to react with lead acetate coated silica gel granules. Presence & amount of gas on the tube is shown by the length of color change on the tube. Read the scale to determine concentration. For your protection, it is advised that you take frequent reading with this type of detector.
Protection
Once the presence of H2S is detected in the atmosphere, the first action to take is to protect yourself against the immediate danger of breathing in the gas by donning a breathing apparatus. As soon as the worker is personally protected, essential employees will be expected to remain in the H2S contaminated areas to do the jobs required to bring the H2S release under control. The remaining personnel should escape to safe briefing areas.
There are three categories of breathing equipment you will find on location.
- Escape Unit
- Work Unit
- Rescue Unit
Escape Unit:
These are located near workstations & accommodation areas. They have a small self-contained air supply & are designed to provide sufficient air about 5-15 minutes to evacuate from a hazardous area & not to work there.
Work Line Unit:
This is used to work in toxic atmospheres immediately dangerous to life or health (IDLH). This would consist of a 5 minutes air bottle with a quick coupling airline connection to a continuous air supply. If necessary the hose can be disconnected & the 5-minute bottle used to leave the hazardous area.
Such equipment is suitable for use in a life-threatening environment.
Rescue Unit:
This self-contained breathing apparatus (SCBA) provides 30 minutes of air. This apparatus provides the user with respiratory protection while performing work in an environment immediately dangerous to life or health. This unit’s regulator is equipped with an alarm that will sound when there are approximately 5 minutes of air left in the bottle. Leave immediately for a safe breathing environment when the low-pressure alarm sounds.
Warning: Eyeglasses should not be worn with a face mask because the temple bars will prevent a facial seal around the mask. Similarly, facial hair could cause an improper face seal. Contact lease should not be worn either as small particles accumulated in the face mask before putting the unit on can blow into the eyes during use, causing severe discomfort.
Emergency Rescue:
The most important part of any rescue attempt in an H2S environment is to protect yourself before attempting rescue. Please remember that cool-headed action in rescue is critical, so do remain calm.
- Put on proper rescue respiratory equipment.
- Move the victim to fresh air at once, upwind or crosswind.
- If the victim is unconscious & breathing has stopped, apply mouth-to-mouth respiration immediately and continue until a resuscitator is brought in, or normal breathing is restored.
- After reviewing the victim, keep him warm & never left him alone.
- Call the doctor.
Artificial Respiration Mouth-to-Mouth Method
Tilt the victim’s head back to open the airway. Place one hand under the victim’s neck, the other on the forehead.
Pinch victim’s nostrils shut with the thumb and forefinger of your hand that is pressing on the forehead.
Seal around the victim's mouth with your mouth. Blow into the victim’s mouth until you see the chest rise. (For infants & small children, seal over & below into both mouth & nose) You should provide at least one breath every 5 seconds, or 12 per minute.
Watch the victim’s chest. When you see it rise, stop blowing. Remove your mouth and look, listen & feel for the air to return & victim chest to fall. When the victim exhalation is finished, repeat the blowing cycle. As the victim attempts to breathe, coordinate your blowing with his breathing.
Artificial respiration should always be continued until the victim begins to breathe for himself or until he is pronounced dead.
Contingency Plans
This is a program of safety measures that plans for:
- Safety prevention & evacuation.
- A plan of action should there be a sudden release of H2S into the atmosphere.
- Emergency procedures for evacuation of all personnel who might be endangered by the H2S.
- First Aid to injured workers.
A Contingency plan should be evaluated on a well-by-well basis. Any well that can produce a concentration of H2S which is 20 parts per million or more should have a contingency plan prepared that should be made to fit actual well & location conditions & should include how severe the concentration could possibly get, & how far they might reach. The contingency plan should include the safeguards for all personnel working on the drilling location & people living in the area around the drill site who might feel the effects of the H2S if it gets into the air. Finally, the contingency plan must obey all Government & Local laws regarding notification, precaution, evacuation procedures & any other rules these bodies required. Make sure you read the contingency plan that has been prepared for your workplace.
Roles and Responsibilities
When Hydrogen Sulfide (H2S) is detected then every effort will be made to ensure the safety of employees & the surrounding general public. To implement this contingency plan a list of essential personnel has been compiled with individual duties and responsibilities.
The essential personnel will be responsible for taking the necessary actions to control the well & reduce the H2S concentration & alerting operation & security personnel should an evacuation be required.
Rig Superintendent
Proceed to Rig Floor to assess the situation & take appropriate actions to control the well.
Mechanical supervisor
Proceed to upwind safe Briefing Area (Muster Point) & standby to shut down equipment if required.
Electrical Supervisor
Proceed to upwind safe Briefing Area (Muster Point) & standby to shut down equipment if required.
Tool Pusher
One tour proceeds to Rig Floor to assess the situation & take appropriate action to control the well at the discretion of Rig Superintendent. Off tour proceed to the upwind safe briefing area (Muster Point) & standby to assist as required.
Driller
On tour stay on the rig floor & take necessary action to control the well. Off tour proceed to upwind safe briefing area (Muster Point) & standby to assist as required.
Assistant Driller
On tour stay on the rig floor & take necessary action to control the well. Off tour proceed to upwind safe briefing area (Muster Point) & standby to assist as required.
Derrickman
On tour stay on the rig floor & take necessary action to control the well. Off tour proceed to upwind safe briefing area (Muster Point) & standby to assist as required.
Cementer
Standby at the safe briefing is (Muster Point) to assist as required.
Mud Logger
On tour stays at the unit to monitor gas unless otherwise instructed off tour to proceed to a safe briefing area (Muster Point).
Radio Operator
On tour, he remains in the radio room. Off tour proceed to the safe briefing area (Muster Point).
Must Remember:
- Not to smoke everywhere at the site, smoke only at designated areas.
- The air must be tested for H2S by a competent person
- If H2S is present, space should be ventilated prior to starting the job.
- If H2S can not be removed, use appropriate respiratory protection & any other Personal Protective Equipment (PPE) rescue & communication equipment.
- If the atmosphere contains 10ppm H2S, it must use respiratory equipment.
- An atmosphere containing high concentrations (Greater than 100ppm)
- are considered immediately risky to life and health (IDHL) & Self-contained
- breathing apparatus (SCBA) is required.
- Be familiar with First Aid procedure, Safe Briefing Area (Muster Area) location & above all.
- All sites must have two Safe Briefing Areas (Muster Point).
- In case H2S is detected, immediately report to a safe briefing area (Muster Area) upwind or crosswind.
- In case of an emergency to whom do you call.
- Hydrogen Sulfide (H2S) odor can be detected at 2ppb (ppb Particle per Billion).
- Make it a point to be always aware of wind direction.
- The breathing apparatus is located at your job place.
- Know what kind of breathing apparatus you need.
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