Classification of hazardous products of hydrogen sulfide

Classification of hazardous products of hydrogen sulfide

1. United Nations GHS classification standards

According to the Global Unified Classification and Labeling System of Chemicals (GHS), hydrogen sulfide (H₂S) falls into the following hazard categories:

1. Physical hazards

• Flammable gas (Category 1)

Hydrogen sulfide can form an explosive mixture when mixed with air at 20℃ and 101.3kPa standard pressure, with an explosion limit of 4.3% to 46% (volume ratio). When exposed to open flames, high heat is extremely prone to flammable and explosion. The combustion reaction equation is:

2H2S+3O2----2SO2+2H2O (elemental sulfur is generated when the air is insufficient: 2H2S+O2-----2S+2H2O)

·Pressed gas (compressed gas)

Hydrogen sulfide is usually stored in a steel cylinder in the form of compressed gas. The pressure inside is ≥200kPa (gauge pressure), which may cause the container to explode when exposed to heat.

2. Health hazards

• Acute toxicity-inhalation (category 2)

Hydrogen sulfide is a strong nerve poison. Inhalation of extremely high concentrations (>1000mg/m³) can cause respiratory and cardiac arrest in a few seconds, which is called "lightning death". The occupational exposure limits are as follows:

◦ OSHA stipulates: 8-hour weighted average 20ppm (28mg/m³), 10-minute peak 50ppm

◦ NIOSH recommendation: 10 minutes upper limit 10ppm (14mg/m³)

3. Environmental hazards

• Hazardous to the aquatic environment - Acute hazard (category 1)

It is extremely toxic to aquatic organisms and can cause lasting pollution to water bodies and the atmosphere.

2. China's classification standards for hazardous chemicals

According to the "Catalogue of Hazardous Chemicals" (2015 Edition) and GB 13690-2009 "General Rules for the Classification and Hazard of Chemicals", the classification of hydrogen sulfide is as follows:

1. Physical hazard classification

• Category 2.1 Flammable Gas

Dangerous goods number: 21006, UN number: 1053, packaging category: O52. Its physical properties are:

◦ Colorless gas, with rotten egg smell (low concentration), and loses the smell due to olfactory nerve paralysis at high concentration

◦ Relative density 1.19 (air = 1), easy to gather in low-lying areas

◦ The self-ignition temperature is 260℃, the minimum ignition energy is 0.077mJ

• Metal corrosives (Category 1)

The aqueous hydrogen sulfide solution is acidic (hydrosulfuric acid), which has a corrosive effect on most metals, especially for metals such as copper and silver, which can form sulfide precipitation:

2. Health hazard classification

• Acute toxicity (category 1)

China's MAC (maximum allowable concentration) is 10mg/m³ (about 7ppm), which is a highly toxic gas. Symptoms of acute poisoning include:

◦ Mild: eye sting, tears, cough, headache

◦ Moderate: Confusion, pulmonary edema

◦ Severe: Lightning death, respiratory arrest

3. Multiple hazards and labeling elements

1. Key hazard labels

• Warning words: Danger

• Hazard statement:

◦ H220: Extremely flammable gas

◦ H280: High pressure gas is installed; it may explode when heated

◦ H330: Inhalation fatal

◦ H400: Very toxic to aquatic organisms

2. Secondary risk

Hydrogen sulfide has both skin corrosion/irritation (Category 1) and severe eye damage/irritation (Category 1), and high concentrations of contact can lead to corneal ulcers and chemical burns in the skin.

4. Safety protection measures

1. Operation requirements

• Strictly enclosed, providing full ventilation, using explosion-proof ventilation systems and equipment

• Stay away from fire and heat sources, smoking is strictly prohibited in the workplace

• Equipped with hydrogen sulfide gas detector (lower detection limit ≤1ppm) and positive pressure air respirator

2. Emergency treatment

• Leak: Immediately evacuate to the upper wind, 150m of small leakage isolation, 300m of large leakage isolation, dilute and dissolve in spray water

• Fire: Cut off the gas source (if possible), extinguish the fire with mist water, dry powder or resistant foam, and use sand and soil caps.

• First aid for poisoning: quickly move to a fresh air place, keep the respiratory tract unobstructed, perform artificial respiration if necessary (no mouth to mouth) and seek medical treatment immediately

5. Regulatory basis

1. United Nations GHS: ST/SG/AC.10/30/Rev.2 (Rev. 2)

2. Chinese standards:

◦ GB 13690-2009 "General Provisions on the Classification and Hazards of Chemicals"

◦ GB 20577-2006 "Flameable Gas"

◦ "Catalogue of Hazardous Chemicals" (2015 Edition) Serial No. 2828

3. Transportation specifications:

◦ UN No. 1053, Dangerous Goods Category 2.3 (toxic gas), Secondary Hazard 2.1 (flammable gas)

◦ Packaging method: Steel gas cylinder, ordinary wooden box outside the frosted glass bottle