You might have heard the term ‘shelf life’ and ‘operational life’ before in reference to electrochemical sensors. They’re the type of terms that lots of people know, but not everybody knows the finer details of what they mean.
How long on the shelf?
For the purposes of this piece, “shelf life” is the time between manufacture of a product and initial operation.
Electrochemical sensors typically have a stated shelf life of six months from manufacture, provided they’re stored in ideal conditions at 20˚C. Inevitably, a small proportion of this period is taken up during the manufacture of the gas detector and in shipping to the customer.
With that in mind, we’d always advise that when acquiring sensors and any spare parts during its lifetime, you plan and time your purchases for minimal delay between storage and usage.
How long in the field?
Again, “operational life” in this context refers to the time from when a sensor starts being used, until it’s no longer fit for purpose.
In absolutely ideal conditions – stable temperature and humidity in the region of 20˚C and 60%RH with no incidence of contaminants – electrochemical sensors have been known to operate in excess of 4000 days (11 years)! Periodic exposure to the target gas doesn’t limit the life of these tiny fuel cells: high quality sensors have a large amount of catalyst material and robust conductors which don’t become depleted by the reaction.
However, absolutely ideal conditions don’t always exist, or stay that way, so it’s vital to err on the side of caution when it comes to gas sensors.
With that in mind, electrochemical sensors for common gases (for example carbon monoxide or hydrogen sulphide) have a typical operational life of 2-3 years. A more exotic gas sensor, such as hydrogen fluoride, may have only 12-18 months.