ExECT1 to T6 Temperature Classes Explained
A temperature class states the equipment’s maximum permitted surface temperature under its rated conditions. T1 corresponds to 450°C, T2 to 300°C, T3 to 200°C, T4 to 135°C, T5 to 100°C and T6 to 85°C.
The temperature-class table
The selected equipment must remain below the ignition temperature required for the explosive atmosphere, with the margin and method required by the applicable standard and site design.
- T1 — 450°C
- T2 — 300°C
- T3 — 200°C
- T4 — 135°C
- T5 — 100°C
- T6 — 85°C
Why T6 is more restrictive
The sequence can feel counter-intuitive: T6 has the lowest maximum surface temperature. Equipment marked T6 therefore satisfies a stricter surface-temperature limit than equipment marked T4, assuming all other conditions are equivalent.
Check the ambient range
A temperature-class marking applies under the conditions covered by the certificate, including its ambient-temperature range. High ambient temperatures, dust layers, installation position or process heating may require additional assessment.
Frequently asked questions
Does T6 mean the equipment operates at 85°C?
No. It is the maximum surface-temperature class, not the normal operating temperature or ambient rating.
Can I select equipment using temperature class alone?
No. Zone or EPL, gas or dust group, protection concept, ambient range and environmental conditions must also match.
Technical guidance only. Always use the product certificate, manufacturer instructions, current applicable standards and a competent hazardous-area professional for a specific installation.