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

Hydrogen sulfide (H2S) is highly toxic to humans, posing serious health risks even at low concentrations, including potential fatalities. Therefore, in environments such as petroleum operations where H2S may be present, it is critical to detect and quantify H2S levels to implement timely protective measures and control emission sources, ensuring the safety of personnel and equipment. Below are common methods for detecting H2S concentrations, aligned with Chinese national standards:

I. National Standard References

1. 《Determination of Toxic Substances in Workplace Air》(GBZ/T 160.33-2004)

• Silver Nitrate Spectrophotometry: H2S reacts with silver nitrate to form colloidal silver sulfide, with concentration determined via spectrophotometric absorbance measurement. Suitable for low-concentration quantitative analysis (0.5–20 mg/m³).

• Gas Chromatography (GC): Utilizes flame ionization detectors (FID) or flame photometric detectors (FPD) for high-precision laboratory testing.

2. 《Design Standard for Detection and Alarm of Combustible Gas and Toxic Gas in Petrochemical Industry》(GB 50493-2019)

• Mandates installation requirements for fixed H2S detectors, recommending electrochemical or semiconductor sensors for continuous monitoring.

II. Nationally Recognized Detection Methods

1. Lead Acetate Detection Tube Method (GB/T 160.33-2004)

• Principle: H2S reacts with lead acetate to form black lead sulfide. Concentration is quantified based on the length of color change in the detection tube.

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• Procedure:

1. Use a dedicated sampler to draw a fixed gas volume (typically 100 mL).

2. Pass the gas through the detection tube; H2S causes lead acetate in the tube to darken.

3. Read the concentration from pre-calibrated scales on the tube.

• Range: 0.5–100 ppm; suitable for rapid on-site screening.

2. Electrochemical Sensor Method (GB 50493-2019)

• Principle: H2S undergoes redox reactions within the sensor, generating a current proportional to its concentration.

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• Features:

• Real-time monitoring with typical ranges of 0–100 ppm.

• Requires regular calibration to avoid cross-interference (e.g., from SO₂ or CO).

3. Spectrophotometry (Laboratory Standard)

• Silver Nitrate Colorimetric Method:

1. Pass sampled gas through an absorption solution (acidic silver nitrate).

2. Formed silver sulfide colloids are measured at 420 nm wavelength.

3. Calculate concentration using a standard calibration curve.

• Sensitivity: Detection limit as low as 0.01 mg/m³, ideal for environmental monitoring.

III. Supplementary On-Site Rapid Detection Methods

• Portable gas detectors:
  Compliant with 《GB 12358-2006》, using electrochemical or photoionization (PID) sensors to display real-time concentrations and trigger alarms.

• Colorimetric Detection Tubes:
  Examples include Dräger or RAE tubes (ISO-compliant), with results read via color comparison charts.

IV. Operational Considerations

1. Sampling Points:

• H2S is denser than air; place detectors at low elevations (0.3–0.6 m above ground).

• Conduct multi-point monitoring in high-risk areas (e.g., oil drilling sites, wastewater treatment plants).

2. Interference Factors:

• Sulfur-containing compounds (e.g., SO₂, mercaptans) may interfere; select anti-interference sensors or apply pre-treatment.

3. Safety Protocols:

• Wear positive-pressure self-contained breathing apparatus (SCBA) during testing.

• Activate emergency procedures if concentrations exceed 10 ppm.

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V. Method Comparison and Applications

VI. Summary

National standards prioritize detection tube methods and electrochemical sensors, supplemented by laboratory spectrophotometry for precise analysis. Practical applications should align with scenarios and adhere to occupational exposure limits (OELs) specified in 《GBZ 2.1-2019》 (MAC = 10 mg/m³). High-risk industries (e.g., petroleum, chemicals) should deploy fixed monitoring systems integrated with portable devices to ensure personnel safety.

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