How Often Should Gas Detectors Be Calibrated?

Set the calibration time for the gas detector, and don’t memorize the hard rule of “once every few months”. This is like asking “how often do you change the oil in a car?” The mechanic will never just look at how many kilometers you have bought the car, but how many kilometers you have run, whether the road conditions are bad or not, and whether the car is old or not. The same is true for a gas detector. Its calibration frequency is alive, which completely depends on whether it is tired every day, whether the environment is bad or not, and its own “physical condition”.

The most reliable way is actually to regard “daily physical examination” as an iron law. This physical examination jargon is called “shock test”. Before starting work every day, blow a bottle of standard gas with known concentration on the instrument. Assuming that the instrument immediately reports to the police, the displayed value is similar to that written on the bottle, and the fault is within the allowable range, it means that the instrument is in good spirits, and it is not necessary to calibrate it at all, so just take it to work. Only when this daily physical examination finds that the instrument is slow to respond, the value difference is outrageous or the coolness is unresponsive, it is necessary to pull it out immediately for “operation”, that is, calibration. Therefore, in many cases, the calibration is not daily, but is “forced” by the daily physical examination results. If you pass the physical examination every day, the number of calibrations will naturally be less; If you fail every day, you may have to calibrate every day, or even consider changing a new sensor.

Of course, even if you pass the physical examination every day, you can’t live without calibration. Sensors, like people, will get old slowly, which is called “drift”. Even if you don’t use it there, the reading will quietly deviate after a long time. In order to prevent this unintentional mistake, manufacturers usually give a “maximum shelf life”. For our common portable all-in-one detector, this period is usually three months to six months. In other words, even if you have a perfect physical examination every day, it is necessary to make a comprehensive calibration for it at the node of half a year, and clear those accumulated minor faults at one time. Assuming that it is a simple instrument that only measures one gas, it may use a particularly stable infrared technology sensor. This period may be longer, but it should not exceed one year.

Environmental factors have the greatest influence on the calibration frequency. Assuming that your instrument is accidentally used in a clean and comfortable studio, it is “long-lived” and calibration can steal some time. However, if you throw it into a coal mine or a local area where the leakage site of a chemical plant may be full of dust and oil, it is simply to let it go to Du Jie. High temperature, high humidity, extremely cold, corrosive gases, these will make the sensor aging and even poisoning failure. In this harsh environment, the calibration period of half a year may have to be compressed to one month or even shorter. Especially when the instrument has been “inhaled” with ultra-high concentration of toxic gas before, it may have accidentally fallen on the ground and bumped against it. No matter when it was calibrated last time, it is necessary to recalibrate it immediately, because its internal parts may have suffered internal injuries by now.

Different “hearts” (sensor types) also have different tempers. At present, the most commonly used electrochemical sensors are specially used to measure oxygen and carbon monoxide. They are delicate and simply affected by temperature and humidity, so they need to be calibrated diligently. Many factories are used to doing it once a month. And that kind of catalytic incineration sensor for measuring combustible gas is especially afraid of silicone and sulfide. Once it is stained, it will be useless, so it should be checked frequently. In contrast, the infrared sensor and photoionization detector are more “real”, with good stability, not simple drift, and the calibration interval can be appropriately lengthened, saving money on buying standard gas.

In the end, we have to look at “family rules” and “royal laws”. Some professions, such as oil exploration and mining operations, may have hard and fast rules in the national safety supervision department. No matter how good your instrument is, it is necessary to calibrate it once a month and leave a paper record, at least once, otherwise it is illegal. At this time, even if you don’t think it is necessary, you have to do it, because compliance is the bottom line of safe operation.

To sum up, the smartest way is to do an impact test every day, which is the first line of defense; According to the manufacturer’s suggestion, set the longest calibration period (such as half a year) as a final and safe one; Look at the environment in the middle, the worse the environment, the more diligent the calibration; Stare at the laws and regulations together, don’t step on the red line. Don’t think of calibration as a form-filling job to cope with errands. It is to ensure that when you are really faced with dangerous gases, the instrument can shout out the alarm for help, instead of blindly reporting numbers or pretending to be crazy. Take the instrument as a companion and understand its temper, so that it can save your life at a critical time.