In a confined space, the safety concentration limit of flammable gases must simultaneously meet the lower explosive limit (LEL) and oxygen concentration requirements. The following are the specific safety standards and protective measures:
一．Core Safety Limits.
1.Concentration of flammable gas
- Safety threshold: ≤ 10% LEL (10% of the lower explosive limit).
- Hazard threshold: ≥ 20% LEL (Stop work immediately and evacuate).
- Explosion range: It will explode upon contact with a fire source when reaching 100% LEL.
2. Oxygen concentration
- Safety range: 19.5% to 23.5% (volume percentage).
- Hypoxia risk: <19.5% May lead to asphyxia; An increase of 23.5% in combustion risk.
二．Work Specifications for Confined Spaces
1. Pre-entry detection
Use a four-in-one gas detector (to monitor O₂, LEL, H₂S, and CO) to conduct multi-point detection at the inlet, middle, bottom, etc. (stratification may occur due to different gas densities).
Qualifying conditions:
- Flammable gas <10% LEL;
-O ₂ is between 19.5% and 23.5%.
Toxic gases (such as H₂S) are below the occupational exposure limit (such as 10 ppm).
2. Continuous monitoring during operation
Fixed detectors are installed at the work site, or the workers wear portable detectors.
If the concentration of flammable gas rises to 10% - 20% LEL, enhanced ventilation is required. Evacuate immediately if the LEL ≥20%.
3. Emergency measures
When the concentration exceeds the limit, activate forced ventilation (explosion-proof fan) or inject inert gas (such as nitrogen).
- Do not use non-explosion-proof instruments or electrical appliances (to avoid sparks).
三．Recommendations for Protective Equipment
1. Testing equipment
Portable: HFP-0401 (can measure LEL, O₂, H₂S, CO).
Fixed detector: HFT-EX (explosion-proof design, interlocking ventilation system).
2. Respiratory protection
When in an oxygen-deficient environment (O₂<19.5%) or with flammable gas ≥10% LEL, a positive pressure air breathing apparatus (SCBA) must be worn.
Portable multiple gas detector is a safety device used for real-time monitoring of the concentration of specific gases in the environment. It is widely applied in industries such as industry, environmental protection, mining, and fire protection to prevent poisoning, explosion, fire and other accidents, ensuring personnel safety and production stability. When choosing a gas detector, it is necessary to match the appropriate model based on specific requirements (such as the type of gas and the usage environment), and regularly calibrate and maintain it to ensure the accuracy of the detection.