Seven Precautions for Hydrogen Sulfide Safety Protection

H2S dangers


1. Extremely dangerous area

The maximum allowable concentration of hydrogen sulfide in the air is 10mg/m3.

When the concentration is greater than or equal to 760mg/m3 (502ppm), people will quickly suffer from acute poisoning, respiratory paralysis and death. This area is extremely dangerous.

2. Highly dangerous area

When the hydrogen sulfide concentration is between 300~760mg/m3 (198~502ppm), it can cause pulmonary edema, bronchitis and pneumonia, headache, dizziness, nausea, vomiting, and dysuria. This area is a highly hazardous area.

3. Moderately dangerous area

When the concentration of hydrogen sulfide is 10mg/m3~300mg/m3 (6.6~198ppm), acute eye irritation may occur, and prolonged exposure may cause pulmonary edema.

It will be in or near the following devices: anaerobic fermentation tanks, sewage tanks, gas holders, desulfurization towers, torch devices, areas along the acid gas pipeline, biogas, waste desulfurizers.

Access to the above-mentioned areas for construction and maintenance must be approved by the workshop, accompanied by a monitoring staff, wear a positive pressure self-contained air respirator, and use a portable hydrogen sulfide detection alarm.


1. Mild poisoning: symptoms such as photophobia, tearing, eye irritation, foreign body sensation, runny nose, burning sensation in the nose and throat, accompanied by dizziness, headache, and fatigue.

2. Moderate poisoning: symptoms such as dizziness, headache, fatigue, nausea, vomiting, unsteady walking, coughing, dyspnea, itchy throat, chest compression, and disturbance of consciousness appear immediately, with strong eye irritation, tearing, and photophobia , Eye tingling.

3. Severe poisoning: manifested as dizziness, palpitations, difficulty breathing, slowness of movement, followed by irritability, confusion, vomiting, diarrhea, abdominal pain and convulsions, quickly entering a coma, complicated by pulmonary edema, cerebral edema, and finally death due to respiratory paralysis.

4. Extremely severe poisoning: Inhalation of 1 or 2 mouthfuls and sudden fall to the ground, instantaneous breathing stops, that is, “electric shock-like” death.


When hydrogen sulfide poisoning accidents or leakage accidents occur, personnel in the contaminated area should quickly evacuate to the windward side, and should call or report immediately, and they should not be handled rashly.

When someone is poisoned and unconscious, rescue personnel must:

1. Wear a gas mask or air respirator, wear a gas suit, and be supervised by two or more people, enter the scene from the upper wind, and cut off the source of leakage.

2. When entering the scene of accidents such as towers, containers, sewers, etc., you must carry your safety belt. If there is any problem, you should evacuate the scene immediately according to the contact signal.

3. Reasonable ventilation, accelerate diffusion, dilute and dissolve hydrogen sulfide with spray water.

4. Move the wounded to a place with fresh air upwind as soon as possible, remove contaminated clothing, keep the respiratory tract open, and give oxygen immediately.

5. Observe the breathing and consciousness of the wounded. If the heartbeat stops breathing, try to perform CPR within 4 minutes as soon as possible (do not breathe mouth-to-mouth).

6. Cardiopulmonary resuscitation cannot be interrupted before arriving at the hospital to start rescue.


1. The production equipment that produces hydrogen sulfide should be sealed as far as possible and set up with automatic alarm devices.

2. Waste water, waste gas, and waste residues containing hydrogen sulfide must be purified and discharged after reaching the emission standards.

3. When entering workplaces such as airtight containers, pits, kilns, and trenches where hydrogen sulfide may be present, the concentration of hydrogen sulfide in the air of the place should be measured first, and ventilation and detoxification measures should be taken to confirm safety before operation.

4. The concentration of hydrogen sulfide in the ambient air of hydrogen sulfide work should be measured regularly.

5. Take personal protective measures during operation, wear gas masks, and tie rescue belts or ropes around the workers’ waists. Mutual insurance should be done, and more than two people should be present, and the poisoned person should be rescued immediately if an abnormal situation occurs.

6. Persons suffering from hepatitis, nephropathy, and tracheitis shall not engage in operations exposed to hydrogen sulfide.

7. Strengthen the training of relevant professional knowledge for employees and raise their awareness of self-protection.


1. Precautions for sampling operation

(1) Check whether the sampler is in good condition;

(2) Wear suitable gas masks, stand in the upper wind, and have special supervision;

(3) During the sampling process, the hand valve should be opened slowly. Do not knock the valve with a wrench.

2. Precautions for water cutting operation

(1) Wear suitable gas masks, have special supervision, and stand in the upper hand;

(2) There should be a certain distance between the dehydration cutting and the dehydration opening;

(3) The released acid gas should be neutralized with calcium hydroxide or sodium hydroxide solution, and isolation measures should be taken to prevent pedestrians from being poisoned;

(4) People cannot leave the scene during the dehydration process to prevent the release of a large amount of acid gas.

3. Maintenance work inside the equipment

It is necessary to enter the equipment and containers for maintenance, generally after purging, replacing, adding blind plates, sampling and analyzing qualified, and getting a safe operation ticket for entering the equipment container before entering the operation. However, some equipment and containers need to be entered to remove residual oil sludge and residue before maintenance. During the cleaning process, toxic and harmful gases such as hydrogen sulfide and oil and gas will be emitted. Safety measures must be taken. The following seven items are the steps for the internal maintenance of the equipment:

(1) Develop a construction plan;

(2) Operators have undergone safety technical training;

(3) Wear a suitable gas mask and carry a seat belt (rope);

(4) Before entering the equipment container for operation, sampling and analysis must be done;

(5) The operation time should not be too long, generally not more than 30min;

(6) Handling safety work tickets;

(7) Special personnel should be supervised during the construction process, and medical personnel should be present when necessary.

4. Enter the sewer (well) and trench for operations

(1) Implement safety protection regulations for working in limited spaces;

(2) Control the dewatering and decondensation of various materials into the sewer;

(3) Use forced ventilation or natural ventilation to ensure that the oxygen content is greater than 20%;

(4) Wear a gas mask;

(5) Carry a seat belt (rope);

(6) Handling safety work tickets;

(7) Special personnel should be set up to supervise the operation underground when entering the sewer and keep close contact with the ground.

5. Cleaning work in the pool

(1) Before the lower tank is cleaned, the sewage must be pumped clean and flushed with high-pressure water for replacement;

(2) Sampling and analysis to determine the safety measures of the construction plan based on the measurement results;

(3) Wear suitable gas masks, have special supervision, and if necessary, bring a seat belt (rope);

(4) Handle the work ticket for limited space.

6. Leakage plugging, disassembly or installation operations

When plugging, disassembling or installing hydrogen sulfide materials in equipment, containers, and pipelines, the following must be done:

(1) Strictly control work under pressure, close the valve communicating with the equipment container, and remove the residual pressure;

(2) Wear suitable gas masks and have special supervision;

(3) When disassembling the flange screws, do not disassemble all the screws before they are loosened, so as to prevent a large amount of toxic gas from rushing out.

7. Precautions for checking production equipment

(1) Operate smoothly and strictly prevent running, leaking, dripping and leakage;

(2) Install a fixed hydrogen sulfide alarm in the device;

(3) Strengthen the maintenance and management of pump equipment to reduce leakage;

(4) Strengthen ventilation in leaking areas;

(5) Vessels, pipelines, valves, etc. containing hydrogen sulfide materials should be regularly inspected and replaced;

(6) If the concentration of hydrogen sulfide is found to be high, it must be reported first, and certain protective measures can be taken before entering the site for inspection and treatment.


When the oxygen content in the air in the workplace is greater than or equal to 20%, and the hydrogen sulfide concentration is less than 10mg/m3, a gray canister filter gas mask can be used. Precautions for using filter gas mask:

(1) Check the air tightness before use: After the user wears the mask, block the air inlet with his hand and inhale hard at the same time. If it feels occluded and airtight, the mask is basically airtight.

(2) Wear it correctly: Choose a suitable specification to make the edge of the cover close to the face. Before use, you should tighten the screws of the air duct and the hood, and connect the other end with the screws of the canister to ensure that all parts are connected tightly and keep the air flowing smoothly. Remember to unplug the bottom of the canister before use. The rubber plug of the air inlet, otherwise it is prone to suffocation accidents. When in use, the vent hole at the bottom of the canister and the exhalation valve of the hood pay attention to prevent the blockage of foreign materials.

(3) Emergency wear: In the event of an accident and cannot leave the scene for a while, the user should hold his breath and quickly take out the hood and put it on. After confirming that the edge of the hood is tightly connected to the head, then exhale the remaining air in the body, and perform a simple air tightness test before putting it into use.


When the oxygen content in the air in the workplace is less than 20%, or the hydrogen sulfide concentration is greater than or equal to 10mg/m3, an isolated gas mask must be selected. Currently, self-contained (air respirators) are commonly used.

Precautions for the use of air breathing apparatus:

1. Perform a pressure test before use: open the cylinder valve and turn the cylinder handwheel counterclockwise for at least 2 turns. Observe the reading of the pressure gauge at the same time, the cylinder pressure should not be less than 28Mpa, otherwise it should be replaced with a cylinder filled with compressed air.

2. Wearing equipment: Fasten and adjust the shoulder strap and waist belt so that the position of the respirator is close to the back of the body. The pressure gauge is fixed on the shoulder strap of the air respirator, and the pressure indication value can be observed at any time to judge the remaining air in the cylinder.

3. Wear a mask: Make sure that an inhalation valve is installed on the mask. Pull the hood and put it on the head, with the strap lying flat on the head and neck, without entanglement. Pull the hood to the back of the head with one hand, making sure that the chin is inside the chin cover of the mask.

4. Check the seal of the mask: Pull the end of the neckband (the two straps below) toward the back of the head to fasten the neckband. Cover the interface of the mask with the palm of your hand, and inhale until negative pressure is generated to check whether the seal between the mask and the face is good. If air is leaking into the mask, remove the mask and wear it again. If the mask cannot be sealed with the face after adjusting, replace it with a new one.

Note: The tight fit of the seal ring of the mask and the skin is the guarantee for the seal of the mask. It must be ensured that there is no hair or beard between the rubber sealing surface and the skin.

5. When the air consumption in the cylinder reaches 5.5MPa±0.5MPa, the alarm will sound to remind the user that there is up to 16% air in the cylinder. Once you hear the alarm, you should be prepared to finish working in the danger zone and leave the danger zone as soon as possible.

Post time: Nov-19-2021