What precautions should be taken when sampling gases?

Gases have the characteristics of being under pressure, permeable, prone to contamination, and difficult to store; therefore, it is necessary to master gas sampling techniques: 1. Stratification in large-diameter pipes and containers can cause uneven distribution of gases, so it is necessary to measure the various points along these surfaces in advance to determine the appropriate sampling locations. 2. For sampling of flowing gases, the flow rate can cause errors; therefore, the flow rate needs to be controlled. 3. Use shorter catheters as much as possible to eliminate errors caused by latency resulting from overly long catheters. To make the gas meet the analysis requirements, it also needs to be filtered, purified, and dried. II. How can we make our samples more representative? 1. Appropriate sampling points should be selected during sampling to avoid samples that are not representative. When the sampling location is unclear, contact the personnel on site promptly so that they can designate the sampling point (for safety analysis, etc.). 2. When sampling, select the appropriate sampling tool based on the conditions of the sample (mainly considering factors such as the sample’s properties and composition). 3. Prepare a detailed sampling record before sampling, and after sampling, attach a label to it. Fill in the information on the label carefully, including necessary sampling details such as the sampling location, location code, name, sampling time, weather conditions, temperature, water level, flow rate, volume flow rate, parameters monitored on-site, and the name of the person who conducted the sampling. 4. When sampling, care must be taken to prevent the inclusion of gaseous substances to avoid sample contamination. For example, when taking samples of boiler superheating, we need to prevent cooling water from splashing in. 5. When the results obtained from sampling are unsatisfactory, it is necessary to keep samples, and records should be made while doing so. III. How to ensure one’s own safety during sampling? 1. When sampling, it is necessary to wear appropriate personal protective equipment based on the conditions at the site; for example, wear frost-resistant gloves when handling low-temperature liquids, and wear gas masks when dealing with toxic gases, and so on. 2. When taking samples, pay attention to the surrounding conditions – check for high-temperature equipment, safety valves, etc., to avoid injuries caused by accidental collisions. 3. When taking gas samples and certain toxic liquid samples, one should stand in the upwind area. 4. If any abnormality is detected at the sampling port during sampling, contact the relevant personnel immediately and inform technicians, etc.; sampling should only be carried out after the issue has been resolved – never attempt to operate it on your own.