What a temperature-sensitive label actually records
A temperature-sensitive (thermochromic) label is a self-adhesive, no-power indicator that permanently or temporarily changes colour once a threshold temperature is crossed. Applied to equipment, a shipment, or a process point, it gives a simple, at-a-glance answer to one question after the fact: did this ever get hotter (or colder) than it should have? That makes it a low-cost complement to — not a replacement for — an active temperature sensor or data logger where continuous readings are actually needed.
Reversible vs non-reversible: pick based on what you need to prove
Non-reversible labels are the more common type: once the threshold is crossed, the colour change is permanent, which makes them a tamper-evident record suited to compliance checks, warranty claims, or proving a cold-chain or shipping-damage excursion happened. Reversible labels change colour above the threshold and change back once temperature drops, which suits ongoing process or equipment monitoring where you want a live visual status rather than a permanent record.
Choosing the range and number of levels
Set the threshold with a defined margin above the equipment's or product's genuinely safe operating temperature, so the label only triggers on a real excursion rather than normal operating variation. Ranges in general industrial use span from single digits and up to roughly +30°C for cold-chain and pharmaceutical shipping, up to well over 100°C for motor, bearing and switchgear overheat monitoring. A single-threshold label gives a simple pass/fail; a multi-level label — some ranges offer up to ten thresholds on one label — additionally shows roughly how high the temperature actually reached, which is useful for judging how serious an overheat event was after the fact.