Given the critical nature of gas detectors, it is important to know they are working correctly at all times. Many factors can affect the performance of gas detection sensors, and all sensors will fail eventually, so users must be vigilant and prepared to change their sensors when required. But changing sensors too early, when they actually have plenty of life left, can be a waste of time and money.
A further issue arises with purchasing and storing spares. Replacement sensors have a finite shelf life, which begins from the moment they are made. As time passes, they can degrade even if kept in ideal conditions (i.e. in a contaminant-free, temperature and humidity controlled environment so the period between purchase and first use should be brief.
So, what should users do to extend the life of their sensors without putting people at risk?
Factors affecting sensor life
The life and/or performance of gas detection sensors can be affected by various factors, including:
- Interfering gases
- Physical factors, e.g. excessive vibration or impact
- Contamination of or damage to the sensor e.g. by incorrect cleaning products
- Contamination of filters or sinters e.g. by dust, sand or pests (yes spiders!)
- Exposure to poisoning/inhibiting compounds even when the sensor is not powered.
There are multiple sensing technologies available and the life expectancy of a sensor is commonly linked to the technology employed. Electrochemical sensors tend to have a shorter life expectancy as compared to Infrared (IR) or catalytic sensors. The type of gas being detected can also have an impact of the life expectancy, the more ‘exotic’ gases (for example chlorine or ozone) tends to be shorter than that of sensors monitoring the more common gases (carbon monoxide, hydrogen sulphide for example).
Most sensors will also suffer general wear and tear, and the damage caused is not always easy to detect, so the first rule for keeping sensors safe and in good working order is to undertake regular maintenance. This should include scheduled bump testing (also known as a gas or functional test) and calibration; while exposure to substantial volumes of gas may harm some sensors, the small amounts used in bump testing and calibration are absolutely fine
It is not always easy to tell that a sensor has failed; some of the techniques suggested are unreliable and this is not an area in which to take risks. The only sure-fire way to know a sensor is working correctly is through application of the target gas(es) in bump testing/calibration.
Planning gas sensor replacement
It makes sense for users to extend the life of their sensors as far as possible; they cost time and money to replace, after all. The ability to forward-plan and predict sensor consumption also makes sensor purchasing more efficient and helps to reduce the time spare sensors are kept in storage.
To predict and plan sensor replacement, users must understand the factors that influence their sensors’ performance. These will be specific to their own setting, which is why users must also be able to draw upon knowledge and experience built up through regular testing and calibration of sensors in their particular environment and applications.
Good quality sensors will come with a warranty, but while this may indicate a general life expectancy there are too many variables and too much at stake for it to stand alone. There really is no substitute for user knowledge and regular maintenance: with these in place, gas detector sensors are far more likely to live long and prosper.