How to conduct gas detection and analysis for confined space operations?
Inspection preparation
Before conducting confined space operations, operators should first clarify the specific tasks, potential hazards, and protective measures to be taken; Secondly, operators should prepare equipment that meets the requirements of national standards, mainly including gas detection equipment, respiratory protective equipment, ventilation equipment, lighting equipment, communication equipment, tripods, safety belts, etc. When there are combustible gases and explosive dust in a limited space, equipment that meets explosion-proof requirements and combustible gas alarm devices should be used; There are also operators who should conduct serious safety checks on the operating equipment, tools, and protective equipment to ensure that the detector is within the validity period of verification, the safety protection equipment is qualified, the test report is complete, the riot prevention equipment has a certificate of conformity, emergency rescue equipment is equipped, and the equipment is running without any faults.
Isolation and clearance
Limited spaces such as pipe wells, sewage tanks, septic tanks, and biogas digesters are all connected to the outside world through pipelines. Toxic and harmful substances from the outside may enter the work area at any time, posing a threat to the safety and health of workers. Therefore, before starting work, it is necessary to separate the work site from the entire toxic and harmful hazardous area through isolation measures, and then take safety protection measures within a limited range to ensure work safety. Close or cut off other pathways where hazardous gases or vapors may flow back into confined spaces, and post warning signs; Take effective measures to prevent the influx of freely flowing substances such as harmful gases, dust, and sewage; Isolate the limited space from all necessary heat sources; Set up necessary isolation areas or barriers, etc.
Before entering a confined space, effective measures should be taken to eliminate or control all hazardous and harmful factors that exist outside the confined space as much as possible. If using a vacuum pump and hose to discharge sludge or accumulated water; Tilt the storage tank to discharge the sludge; Emptying using the discharge port at the bottom of the tank; Using water vapor, inert gas pressure cleaning, and forced ventilation from outside a limited space.
After the above measures are completed, before entering the confined space, it is necessary to detect and analyze the potential hazards of the confined space based on the working site and surrounding environment, determine whether the concentration of toxic and harmful gases exceeds the standard, and evaluate the degree of danger in the working environment, and take targeted protective measures. The detection indicators include oxygen concentration value, concentration value of flammable and explosive substances (flammable gases, explosive dust), concentration value of toxic gases, etc. Without testing, one cannot enter a confined space. The following points should be noted during testing:
● Detect startup. After booting and self checking in a clean environment, check if the instrument has power. If the battery is found to be low, immediately replace it in a safe environment or activate another detection alarm device.
● Initial environmental detection of oxygen, combustible gas, and toxic gas concentrations. Oxygen concentration, whether in oxygen deficient or oxygen rich environments, is very dangerous to the safety and health of workers. In addition, the sensors equipped with detection instruments need to be at a certain oxygen concentration to work properly; When the concentration of combustible gas in a generally limited space reaches or exceeds 20% of its lower explosive limit, entry is prohibited; When a gas has both toxic and explosive properties, the concentration value corresponding to the harm caused by the substance should be compared and a lower value should be selected for detection.
● Detection point settings. The correct selection of detection location is necessary to ensure the detection of the entire limited space, otherwise potential gas hazards may not be detected due to missed detection in certain areas or locations, leading to accidents. The detection point includes the entrance and exit of a limited space, especially when the limited space is just opened, this position should be detected first; Limited space input pipeline entry point; The location where personnel carry out work; Different height positions within a limited space; And at the location where gas (vapor) may accumulate.
● Timing of testing. Gas detection should start before the operation and continue throughout the entire process. Pre job inspection, opening the entrance and exit cover plate of the confined space, ventilation, cleaning, and blowing out the confined space, and before entering the new workplace, all inspections are required; Real time detection during operation. Due to the complexity of the internal environment and operation in a limited space, it is necessary to continuously detect changes in the concentration of toxic and harmful gases in the limited space and take necessary measures at any time during the operation process.
● Inspection records. Truly record all test results, including the type and concentration of hazardous gases; Presence location, required air volume.
