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Maintenance and calibration of gas detectors

Gas detectors are an important safety measure in households, industries, but also in workplaces and car parks and garages. In some countries, the use of detectors is mandatory, in other countries it is a voluntary decision of the property owner or operator that helps protect lives, health and property. Detectors differ mainly depending on what gas they detect and in which environment they are placed. Regular maintenance and calibration are always necessary for their correct function.

Introduction: Glossary

In this article, we will introduce some key terms that will help guide you in calibration of gas detectors in your household or elsewhere.

  • Calibration is the first setting of sensor limits, which is performed during production and its output is a calibration protocol. Simply put, calibration determines signaling limits of the gas concentration at which the detector alarm is triggered.
  • Recalibration is a re-comparison of measured values against a standard.
  • Calibration gas intended for this is considered as a standard. It is usually a calibration gas with an issued certificate of concentration accuracy. Using the calibration gas, reference value of the gas concentration is stored in the detector's memory.
  • Sensor is its own sensing element that converts the chemical concentration of the measured gas into an electrical signal. 

Why and how often is it necessary to calibrate detectors?

Since sensors work with chemical and physical changes in materials, it is logical that they are subject to aging and gradually lose their sensitivity to gas. This is the reason for recalibrations. Over time, each sensor measures a little differently, so it is necessary to compare measured values.

So how often do detectors need to be recalibrated to function properly? Please refer to your local regulations, which stipulate the conditions of fire safety in your area. The specific recalibration frequency is further regulated by the installation and operating instructions and the operating instructions issued by the safety technician in the given application.

The adjustment of the minimum recalibration frequency in the manual is determined on the basis of the sensor used. For conventional electrochemical and semiconductor sensors, it is usually 6-12 months. For more robust types of sensors, such as optical NDIR sensors, the minimum interval is longer, from 1 to 5 years. The lifetime data is therefore only an approximate estimate based on experience. The actual service life is different for each piece and application.

EVIKON gas detectors require regular maintenance and calibration.

What affects the life of sensors?

It is very different for everty sensor, depending on humidity, temperature, dust, frequency of exposure and many other factors. Prolonged exposure of the measured gas can even destroy some sensors. As well as exposure of gases with a concentration greater than the range of the sensor. This often happens when using detectors near sinks or when disinfecting and cleaning.

In addition, most sensors are not selective and detect a wide range of gases. Thus, even if the detector is calibrated, for example, to detect methane, it can simply be destroyed by an open can of paint near the detector. Solvent fumes then enter the sensor, triggering a false alarm and soon oversaturating and destroying it.

Sensor's aging can be slowed down by disconnecting it from the power supply. An unplugged sensor ages much slower than a powered one. It is therefore possible to store the detectors for up to 6 months without recalibration and still perform the first recalibration after 12 months from plugging in.

How to recalibrate and maintain gas detectors

As mentioned above, maintenance and recalibration of detectors is usually mandatory by law and if you do not comply with this obligation and the procedures set by the manufacturer, you may lose not only the warranty, but also the right to indemnity in the event of an insured event.

Maintenance of gas detectors varies according to their type and manufacturer. For example, Honeywell small home detectors are not calibrated, but are discarded at the end of their service life. For other types following is necessary:

  • regular recalibration,
  • sensor replacement at the end of its service life,
  • regular functional tests and inspections of the protective dust filter.

The minimum intervals for these are always specified by the manufacturer and must be met. Service, functional tests and calibration of gas detectors may only be performed by qualified professionals and services authorized by the manufacturer.

In addition to calibration, do not forget to regularly inspect gas and your gas appliances, the cost of which is negligible compared to the risk of explosion.

Honeywell small detectors are simply discarded at the end of their service life.

Recalibration of gas detectors

The method varies depending on the type of detector and manufacturer. Evikon detectors are calibrated annually and require calibration gas and calibration software. There are two ways to recalibrate these detectors. The first is the correspondence recalibration. The operator disassembles the detector and sends it to the manufacturer or distributor for recalibration. They feed and recalibrate it for 48 hours. After recalibration, they send it back to the operator. The second option is to contact one of the trained calibration partners. These are companies throughout the Czech Republic that are trained to perform recalibrations and have the necessary equipment.

Detectors from other manufacturers use their own software, and some manufacturers only tune the potentiometer with a screwdriver. In any case, the detector must be connected to the power supply for at least 24 hours, but preferably 48 hours and longer, before recalibration. This heating of the sensor is necessary to achieve the stability of the measurement, which is needed for its recalibration.

Sensor replacement

The sensor may only be replaced by a trained person. Exceptions are semiconductor, optical, and photoionization sensors that are replaced by the manufacturer because they require tampering with the detector firmware. Electrochemical and catalytic sensors can be replaced simply by disconnecting the connector. After replacing the sensor, it is necessary to calibrate the detector.

Functional test

In addition to regular recalibrations and sensor replacements, functional tests are also performed. The first is during the installation of the device, after starting and stabilizing the measurement, test gas is released on the sensor and the detector's response is monitored. Further functional tests may be performed by the safety technician in an internal regulation.

Check the protective dust filter

During the functional test and recalibration, the protective dust filter, which protects the sensor, is also checked for clogging. Running detectors without this filter reduces their life and will void the warranty. The filter is made of a special several-layer laboratory paper. At the same time, it often happens that customers confuse it with a plastic cover and throw the filter away.