Quick answer
First follow the site emergency plan if there is an alarm or suspected gas release. Otherwise, preserve the reading trend and confirm the warm-up requirements for the installed model before labelling the change as calibration drift. Record environmental and operating context, service history and controller observations. Do not zero or adjust the instrument simply to make the displayed value stable.
Describe the change before naming its cause
Write down whether the value rises steadily, falls, fluctuates or changes in steps. Include its unit and the elapsed time from the recorded start-up event. 'The reading changed after start-up' is an observation; 'the sensor has calibration drift' is a diagnosis that needs further evidence.
Confirm which stabilization requirement applies
Request the manual revision for the installed sensor and detector configuration. Ask the service reviewer which start-up and stabilization requirements apply to the observation being evaluated. Do not borrow a countdown from another model, or assume a previous replacement has the same requirements as the original equipment.
MSA's PrimaX IR+ start-up documentation distinguishes output availability from stabilization before calibration. This manufacturer-specific example shows why those events should not be treated as synonymous; its durations are not UTAI specifications.
Collect context without creating a new exposure
Use records and observations already accessible under safe site arrangements. State what was actually recorded about process operation, ambient conditions, recent cleaning or maintenance, and power events. Leave missing information blank or label it unknown; do not insert assumed temperature or humidity values based on the location.
If a local reading and a controller trend are both available, identify their point labels and timestamps. Ask the reviewer whether the observations represent the same period. Avoid comparing a current display with an undated screenshot as though they were simultaneous measurements.
Keep measurement and electrical review distinct
MSA's PrimaX IR+ troubleshooting table includes supply condition and electrical noise among checks for an unstable output after warm-up. It is an example of a wider diagnostic review, not proof that a particular UTAI symptom has an electrical cause.
Send the original trend to qualified support with the last service result and known equipment changes. Ask which evidence would distinguish the possible explanations. This page does not authorize live measurements, opening an enclosure, changing wiring, cleaning a sensor or adjusting calibration.
Close the investigation with an evidence statement
A useful outcome states whether the change was reproduced, what was established and what remains uncertain. 'Not reproduced during review' is different from 'cause confirmed and corrected'. Ask the responsible person to record the applicable verification and operational decision, not just a final photograph showing a steady number.
The UTAI maintenance guide provides the wider maintenance-planning context. This article adds a trend-focused support brief. It supplies no permitted drift tolerance, universal warm-up time or automatic-zero recommendation, and it is not clearance to keep operating with uncertain monitoring.