Dust Surface Temperature Checker
Compare a marked surface temperature with a cloud and 5 mm layer screening limit. Use test data for the actual dust; gas T-classes are not dust temperature ratings.
Screening only. This tool does not classify hazardous areas or approve a product, installation or safety system. Use the applicable project requirements, manufacturer data and exact certificate conditions.
Method & limits
Cloud limit = cloud ignition temperature in °C × 2/3. Layer limit = 5 mm layer ignition temperature in °C - 75 K. The smaller value controls. A marked temperature equal to the calculated limit passes this numerical screen. Layers over 5 mm suppress a PASS/FAIL decision and require further assessment; Layer ignition temperatures below 250°C require laboratory verification under the cited selection guidance, even when the numerical comparison passes. This simple rule does not account for thick deposits, complete burial, special marked layer conditions or self-heating dust.
Frequently asked questions
Which temperature controls?
The smaller of two-thirds of the cloud ignition temperature and the 5 mm layer ignition temperature minus 75 K.
Can a gas T4 marking be used instead?
No. Enter the actual maximum surface temperature marked for dust service and check its certificate conditions.
Is equality a pass?
Equality passes this arithmetic comparison. It does not prove that the test data, deposit assumptions or equipment conditions apply.
What if the layer is thicker than 5 mm?
The tool returns specialist review and does not approve the equipment using the 5 mm calculation.
Does the tool determine Zone 20, 21 or 22?
No. Dust area classification, conductivity, deposits and installation suitability require the project assessment.
Sources & verification
Source and calculation review: 2026-11-05. Reference methods do not replace the edition adopted for your project.