Chlorine dioxide (ClO₂) is a yellow-green gas with oxidizing power stronger than chlorine, used across many industries — tap-water disinfection, food sterilization, paper bleaching, and HVAC-system sanitization. But even trace amounts around 0.1 ppm irritate the mucous membranes of the eyes, nose, and throat, and high-concentration exposure can cause acute pulmonary edema, making thorough gas monitoring essential. The WANDI EDW500 is a portable multi-gas detector holding IECEx international explosion-proof certification (Certificate: IECEx TPS 25.0057X, certifier: TÜV SÜD); it simultaneously measures up to 5 gases including ClO₂ to protect workers' lives on site.
What Is Chlorine Dioxide (ClO2)?
Chlorine dioxide is a yellow-green gas with the formula ClO₂ and a molecular weight of 67.45. It is unstable at room temperature and can decompose explosively under light, heat, or shock. Highly soluble in water and strongly oxidizing, it is widely used as a disinfectant and deodorizer in water treatment facilities and food plants worldwide.
💡 Key Point
ClO₂ is about 2.6 times more effective at disinfection than chlorine (Cl₂), but its permissible exposure limit (TWA 0.1 ppm, ACGIH) is very low, so even trace amounts pose a poisoning risk.
Health Effects of Chlorine Dioxide
| Concentration (ppm) | Exposure Time | Health Effect | Risk Level |
|---|---|---|---|
| 0.01 | Continuous | Odor detectable (characteristic chlorine smell) | Watch |
| 0.1 | 8 hr (TWA) | Eye/nose/throat mucous irritation, coughing | Caution |
| 0.3 | Short-term (STEL) | Severe respiratory irritation, headache, nausea | Danger |
| 1–5 | Short-term | Pulmonary edema, severe bronchospasm | Severe Danger |
| 10+ | Immediately | Life-threatening, acute respiratory failure | IDLH |
※ Source: ACGIH TLV-TWA 0.1 ppm, NIOSH IDLH 5 ppm, OSHA PEL 0.1 ppm (8-hour TWA)
Sites at Risk of Chlorine Dioxide Leaks
ClO₂ leak risk is especially high at the following sites: ① water purification and water/wastewater treatment facilities, ② sterilization processes in food and beverage manufacturing plants, ③ bleaching areas of paper and pulp mills, ④ routine disinfection of cooling towers and HVAC systems, and ⑤ storage warehouses for ClO₂-generating chemicals.
Real Accident Cases
ClO₂ Leak at a Texas Water Treatment Facility, USA (2019)
At a municipal water treatment facility in Texas, USA, a ClO₂ generator malfunction released a large volume of gas. Three on-site workers were hospitalized with acute respiratory irritation, and part of the facility was shut down for 24 hours. The causes were a defect in an aged pipe joint and the absence of real-time gas monitoring.
※ Source: U.S. Chemical Safety and Hazard Investigation Board (CSB) incident report, 2019
ClO₂ Poisoning at a Domestic Food Plant, Korea (2021)
At a food manufacturing plant in Gyeonggi Province, two workers experienced headache and nausea during ClO₂ disinfectant dilution work due to insufficient ventilation and stopped work — a case reported to the Korea Occupational Safety and Health Agency (KOSHA).
※ Source: Korea Occupational Safety and Health Agency (KOSHA) chemical incident casebook
WANDI EDW500 — IECEx-Certified 5-Gas Simultaneous Measurement
(TÜV SÜD, IECEx TPS 25.0057X)
(hazardous gases including ClO₂)
automatic data logging
The EDW500 holds the Ex da ia IIC T4 Ga (Zone 0, EPL Ga) explosion-protection rating, allowing use even in the most hazardous explosive zones. Beyond ClO₂, it measures a total of 5 gases at once — O₂, CO, H₂S, and combustible gas (EX) — making it the optimal safety solution for water treatment, food, and paper plants where multiple hazards coexist.
Installation Cases
What If WANDI EDW500 Had Been Used? Prevention Scenario
- 1Pre-measurement: Before inspecting the ClO₂ generator, measure the work-area ClO₂ concentration in advance with the EDW500.
- 2Real-time alarm: The moment ClO₂ exceeds 0.1 ppm (the alarm setpoint) during work, a powerful sound/vibration/LED alarm fires immediately.
- 3Immediate evacuation: With the alarm, the worker evacuates at once, and an automatic notification is sent to the manager via the IoT cloud.
- 4Data logging: All measurement data is saved automatically, serving as legal evidence and a basis for Serious Accidents Punishment Act compliance.
EDW500 Key Specifications (ClO₂ Measurement)
| Item | Specification |
|---|---|
| Explosion-proof cert. | IECEx TPS 25.0057X (TÜV SÜD) / Ex da ia IIC T4 Ga |
| Simultaneous gases | Up to 5 (ClO₂, O₂, CO, H₂S, EX, etc. combinable) |
| ClO₂ measurement range | 0 ~ 1.0 ppm (resolution: 0.01 ppm) |
| Alarm method | Triple alarm: sound (95 dB) + vibration + LED flash |
| IoT integration | Real-time cloud monitoring, automatic data logging |
| Battery | 12+ hours of continuous use |
A Closer Look at the WANDI EDW500
Below are real photos of the WANDI EDW500 portable multi-gas detector and its use on site.
