Detection methods for limited space gas detectors
Using a limited space gas detector to detect confined spaces requires first checking if it is within a safe range when working in these spaces. Which gas detector is more suitable? The selection of gas detectors first requires a clear understanding of the gas, and then sensors with different principles are used based on the physical and chemical properties of different gases.
1. If there is accumulated water or mud in a confined underground space, tools should be used to thoroughly mix it outside the confined underground space.
2. Testing personnel should stand at the upper air vent, and evaluation testing, admission testing, and monitoring testing should be conducted outside the confined underground space.
3. Different monitoring points, starting from the entrance, from top to bottom, and from near to far.
4. Detect different gases at the same monitoring point based on the order of oxygen, combustible gases, and toxic gases.
5. The detection time at each point should be greater than the response time of the instrument, and the ventilation time of the sampling tube should be increased.
6. Each gas at each detection point should be continuously detected three times, based on the highest value of the detection data.
7. The interval between two tests should be greater than the recovery time of the instrument.
8. During testing, if the detection value exceeds the measurement range of the instrument, the instrument should be immediately separated from the sampling and flushed with fresh air for 5 minutes. After returning to zero, the next detection can be carried out. If the detector malfunctions and alarms, the detection should be stopped immediately.
Finally, limited space operations should strictly follow the principle of "ventilation first, testing later, and operation later". The detection indicators include oxygen concentration, concentration of flammable and explosive substances (combustible gases, explosive dust), and concentration of toxic and harmful gases. The testing should comply with relevant national or industry standards. Without passing the ventilation testing, no personnel are allowed to enter the confined space for operation, and the testing time should not be earlier than 30 minutes before the start of the operation.
