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There is no thermometer symbol. The elevated-temperature marking is the word HOT shown in an upward-pointing triangle, used for materials transported at high temperature, such as molten substances. People expect a thermometer graphic, but the actual mark is simply HOT in a triangle, which is the difference to learn.
The marking is a word, not a picture
The instinct is to imagine a thermometer to mean hot, but the transport system does not use one. For materials moved at an elevated temperature, the marking is the word HOT, displayed inside an equilateral triangle pointing up. It is plain and text-based on purpose, so it reads instantly at a distance.
What it warns about
The HOT marking flags materials carried hot enough to injure or to behave dangerously, classic examples being molten sulfur, molten aluminum, or hot asphalt. The danger is the temperature itself: contact burns, and the way a hot load can react if it contacts water or spills. The mark tells responders to treat the contents as thermally dangerous, separate from any chemical hazard class.
HOT marking at a glance
The facts worth memorizing:
| Item | Detail |
|---|---|
| Form | The word HOT in an upward triangle |
| Not | A thermometer graphic |
| Means | Material transported at high temperature |
| Examples | Molten sulfur, molten metal, hot asphalt |
| Type | A marking, not a hazard-class placard |
The elevated-temperature mark is the word HOT, not a thermometer. Confirm the exact form and thresholds in the regulations.
Why it is not a placard color
Elevated temperature is not one of the nine hazard classes, so it does not get a colored diamond. Instead it is an additional marking that can appear with or without a separate hazard-class placard, depending on the material. That is why you should not look for a temperature color; you look for the HOT triangle.
How to study it
Remember the shape and the word together: an upward triangle with HOT inside. If a question offers a thermometer image, it is the wrong answer by design. Pair this marking in your study with the idea of molten or hot loads so the concept sticks. The exact temperature thresholds and when the mark is required are defined in the regulations, so verify them there and in your official manual.
Frequently asked questions
- What is the HOT mark on a truck?
- It is the elevated-temperature marking: the word HOT inside an upward-pointing triangle, used for materials carried at high temperature like molten substances. There is no thermometer symbol. Confirm the exact form in the regulations.
- Is there a thermometer placard for hot materials?
- No. The marking is the word HOT in a triangle, not a thermometer graphic. Expecting a thermometer is a common mistake.
- Is elevated temperature a hazard class?
- No, it is not one of the nine classes, so it has no colored diamond. It is an additional marking that can appear alongside a hazard-class placard.