National Standard Detection Methods for Hydrogen Sulfide (H₂S) gas leak detector

Hydrogen sulfide (H₂S) is highly toxic to humans and poses significant health risks even at low concentrations, potentially leading to severe health complications or fatalities. Therefore, in environments such as petroleum operations where H₂S may be present, it is imperative to detect and quantify its presence and concentration. This enables timely implementation of protective measures, control of emission sources, and ensures the safety of personnel and equipment. Below are common methods for detecting H₂S concentrations in accordance with Chinese national standards:

1. Lead Acetate Test Paper Method

• Procedure:

• A white test paper is coated with a lead acetate solution. If the paper remains white, no H₂S is present. Upon exposure to H₂S, the paper turns brown or black.

• After exposing the test paper to ambient air for 3–5 minutes, the H₂S concentration is determined by comparing the color change to a standard chromatographic reference.

• Note: The test paper must be moistened before use.

• Reagent Formula: 10 g of lead acetate dissolved in 100 mL of distilled water.

• Reaction Principle:

  $${\text{Pb(CH}}_3{\text{COO)}}_2+{\text{H}}_2\text{S}\to \text{PbS (brown/black)}+2{\text{CH}}_3\text{COOH}$$Pb(CHCOO)+HS→PbS (brown/black)+2CHCOOH

• Application: Qualitative analysis.

2. Ampoule Method

• Procedure:

• A sealed ampoule contains white lead acetate (Pb(CH₃COO)₂) solid granules, with a porous sponge plug.

• H₂S gas diffuses through the sponge and reacts with the granules, turning them black.

• Analysis: The degree of blackening is used for qualitative or semi-quantitative measurement.

3. Detection Tube Method

• Procedure:

• Requires skilled operation for reliable results.

• Measurement precision depends on operator expertise.

• Pre-manufactured detection tubes (commercially available) contain lead acetate-impregnated solid granules.

• When H₂S-contaminated air is drawn through the tube, the length of the darkened section corresponds to the H₂S concentration, which is read directly from pre-calibrated scales on the tube.

• Advantages: High accuracy and low cost.

• Limitations:

  
  

Key Notes

1. Safety Precautions:

• Use personal protective equipment (PPE) such as gas masks or SCBA (self-contained breathing apparatus) in H₂S-prone areas.

• Immediate evacuation is required if concentrations exceed 10 ppm (OSHA permissible exposure limit).

2. Interference Management:

• Avoid cross-interference from other sulfur compounds (e.g., SO₂, mercaptans) by selecting appropriate detection methods or pre-treatment steps.

3. Standards Compliance:

• Follow guidelines from GBZ/T 160.33-2004 (workplace air quality) and GB 50493-2019 (petrochemical gas detection) for method validation and equipment calibration.

Summary

These methods—test paper, ampoule, and detection tube—are widely adopted for rapid on-site screening of H₂S in industrial settings. While the detection tube method offers higher precision, proper training is critical to mitigate operational errors. For laboratory-grade accuracy, supplementary techniques like gas chromatography or spectrophotometry (referenced in national standards) are recommended.

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