How Gas Detector Sensors Age: Understanding Drift and When to Recalibrate

Every gas detector loses accuracy over time. It is not a defect, it is chemistry. Sensors are consumable components, and understanding how they age helps EHS teams calibrate on the right schedule instead of guessing. A detector that reads fine on the display can still be drifting quietly toward an inaccurate result, and the only way to know is regular verification.

What "drift" actually means

Drift is the gradual change in a sensor's output when the actual gas concentration hasn't changed. A sensor that once read exactly 25 ppm against a 25 ppm reference might read 22 or 28 ppm months later. Small drift is normal; the job of calibration is to catch it and correct it before it grows large enough to matter.

Why sensors age

Different sensor types age for different reasons:

• Electrochemical sensors rely on a chemical reaction that consumes reactive material over time. Exposure to the target gas, temperature extremes, and very dry or very humid air all shorten their life. Most electrochemical cells last two to three years , less for reactive gases like ozone or chlorine.
• Catalytic bead (LEL) sensors can lose sensitivity or be poisoned by silicones, sulfides, or lead compounds, sometimes suddenly rather than gradually.
• Photoionization detectors (PID) drift as the lamp window fouls and UV output weakens.

What accelerates drift

Beyond normal aging, several field conditions speed things up: repeated exposure to high gas concentrations, temperature swings, humidity extremes, physical shock, and long periods of storage. A sensor sitting unused isn't "resting" — many continue to age on the shelf.

Catching drift before it's a problem

The defense against drift is a two-part routine most safety programs already know:

• Bump test before each day's use to confirm the sensor and alarms respond to gas. ISEA recommends verification before each day the instrument is used.
• Full calibration on a set interval to correct the reading against a known concentration. Many programs keep the interval between checks to no more than 30 days unless their data supports a longer one.

Recording as-found and as-left values at each calibration turns drift into a visible trend line. When a sensor needs bigger and bigger corrections to hit the reference, it is telling you it is near end of life, and you can replace it on your schedule instead of during an audit or an incident.

Keep calibration simple

The easier calibration is to perform, the more consistently it gets done. On-demand gas generation gives technicians a fresh, known concentration whenever they need it, with no cylinders to track, expire, or ship. Browse GoACD's calibration gas generators to build a routine your team will actually keep up with.