Temperature limit (thermometer between limit lines)
The standard’s wording, as the sources below reproduce it:
“Indicates the temperature limits to which the medical device can be safely exposed.”
ISO 15223-1:2021, 5.3.7 (with 5.3.5 and 5.3.6) · ISO 7000-0632
What it means for you
Keep the device between the two printed temperatures. With 2 °C by the lower line and 30 °C by the upper one, anywhere from 2 °C to 30 °C is inside the limit: a room at 21 °C is fine, a parked car at 50 °C in summer or a shed at −5 °C in winter is outside it. If it has been outside the range — left in a hot car, frozen in the post — check the instructions for use or ask the pharmacist or supplier before using it.
Whether a device is right for you is a question for your pharmacist, nurse or doctor.
- What it looks like
- A thermometer with a short horizontal line at its top right and another at its bottom left, each with a temperature printed next to it.
- Where you see it
- Boxes of blood-glucose and other test strips, pregnancy and COVID test kits, laboratory reagents, sensors, dressings and shipping cartons of sterile products.
- Other names
- store between; upper limit of temperature; lower limit of temperature
What it does not tell you
It does not say how long the device may spend outside the range or whether it still works after being too hot or too cold — only the instructions or the maker can say that. It is not a heat-resistance rating.
How to read the two figures
Example: 2 °C to 30 °C. The figure beside the upper line is the highest temperature, the figure beside the lower line the lowest. BÜHLMANN’s glossary quotes the rule: “The upper and lower limits of temperature shall be indicated adjacent to the upper and lower horizontal lines.” So this drawing reads “store between 2 °C and 30 °C”; the thermometer itself carries no scale.
With only one line: upper or lower limit
Upper limit of temperature · ISO 15223-1:2021, 5.3.6 (ISO 7000-0533). Only the top line, with one figure: keep the device at or below that temperature. It sets no lower limit.
Lower limit of temperature · ISO 15223-1:2021, 5.3.5 (ISO 7000-0534). Only the bottom line, with one figure: keep the device at or above that temperature. It sets no upper limit.
The same drawing elsewhere on semiatic
The kitchenware temperature mark means heat resistance: On a food box or dish a thermometer with figures is the maker’s own statement of the hottest and coldest the item withstands; on medical packaging the thermometer between limit lines is an ISO 15223-1 limit for the device itself.
More symbols in “Limit lines”
Sources
ISO 15223-1 is a paid standard, so the wording above is quoted as 3 publishers’ public documents reproduce it. Each was fetched and read on the date shown:
- Boston Scientific: Symbols Glossary — ISO 15223-1 5.3.5 “Lower limit of temperature”, 5.3.6 “Upper limit of temperature” and 5.3.7 “Temperature limit — Indicates the temperature limits to which the medical device can be safely exposed”, images labelled ISO 7000-0534, -0533 and -0632. Checked 2026-09-25.
- NE Scientific: Master Symbol Glossary (CTF-100011 Rev 01) — Shows the thermometer with limit lines for reference nos. 5.3.5 (ISO 7000-0534), 5.3.6 (ISO 7000-0533) and 5.3.7 (ISO 7000-0632). Checked 2026-09-25.
- BÜHLMANN Laboratories: Symbol glossary, version 03 (release date 2025-02-04) — “Temperature limit — Indicates the temperature limits to which the medical device can be safely exposed. The upper and lower limits of temperature shall be indicated adjacent to the upper and lower horizontal lines.” Checked 2026-09-25.
Plain-language parts are in our own words; quotations are the sources’ wording.