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Frequently Asked Questions
Why are sensors treated as consumables?
Every sensing technology degrades, and the degradation is gradual and invisible.
Electrochemical cells are chemically consumed by the reactions they measure.
Catalytic beads are poisoned and lose catalytic activity.
Infrared sources age and optics contaminate.
A sensor at end of life still produces a reading - just a wrong or slow one.
Budgeting and scheduling replacement is part of owning the system rather than an unexpected cost.
What is the difference between a bump test and a calibration?
A bump test proves the system is alive; a calibration proves it is accurate.
A bump test applies test gas briefly and confirms response and alarm operation.
A calibration adjusts the instrument against a known concentration.
Bump tests are quick and frequent; calibrations are slower and less frequent.
Neither substitutes for the other, and both are normally required.
The manufacturer gives one interval and the regulations another; the shorter one wins.
How much does the environment affect sensor life?
Substantially - stated life assumes benign conditions that many installations do not provide.
High temperature accelerates chemical degradation in electrochemical cells.
High humidity and condensation affect several technologies.
Continuous exposure to the target gas consumes an electrochemical cell faster.
Contaminants poison catalytic sensors and coat optical windows.
A wet, hot, dirty installation should expect shorter life than the datasheet figure.
What are replaceable sensor modules?
Sensor assemblies that can be swapped in the field without recertifying the whole detector.
They turn replacement from a project into a routine maintenance task.
Pre-calibrated modules reduce time spent at height or in a hazardous area.
Some designs still require a post-fit calibration check.
Module compatibility is specific to the detector and not interchangeable.
In hazardous areas the replacement procedure must not invalidate the equipment's certification.
Can a failed calibration be the test gas rather than the sensor?
Yes, and it is a common and frustrating cause.
Cylinders have expiry dates that are frequently overlooked.
Some gas mixtures are unstable at low concentrations and drift over time.
Reactive gases can be absorbed by cylinder walls, regulators and tubing.
Tubing material and length affect reactive gases measurably.
Checking the gas before condemning the sensor saves replacing working instruments.
How is the flow of test gas applied?
Through a calibration adapter at a controlled flow rate, using tubing suited to the gas.
Too little flow starves the sensor and gives a low reading.
Too much can pressurise the sensor and distort the result.
Adapters are detector-specific and are part of the maintenance kit.
Reactive gases need inert tubing, since ordinary tubing absorbs them.
Manufacturers specify flow rates and adapter types for each detector.
What records should be kept?
Calibration and bump test results, sensor serial numbers and replacement dates, and test gas details.
Records are what an inspector asks for and what demonstrates the system is maintained.
Trending calibration drift over time predicts failures before they occur.
Sensor replacement dates allow life to be tracked against the environment.
Test gas cylinder details link a suspect result to a possible gas problem.
How long to keep records, and in what form, comes from the regulations and from the site's own management system.