Category calculator
Enter the flash point. Below 23 °C the initial boiling point is needed as well. The calculation runs in your browser; nothing is sent anywhere.
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CLP criteria
| Category | Criterion | Hazard statement | Signal word | Example |
|---|---|---|---|---|
| Category 1 | FP < 23 °C and initial boiling point ≤ 35 °C | H224 Extremely flammable liquid and vapour | Danger | Diethyl ether |
| Category 2 | FP < 23 °C and initial boiling point > 35 °C | H225 Highly flammable liquid and vapour | Danger | Acetone, toluene, ethanol, ethyl acetate |
| Category 3 | 23 °C ≤ FP ≤ 60 °C | H226 Flammable liquid and vapour | Warning | Xylene, n-butanol |
| Not classified | FP > 60 °C | – | – | Hydraulic oil, cutting oil |
Regulation (EC) No 1272/2008 (CLP), Annex I, 2.6. Note to Table 2.6.1: gas oils, diesel and light heating oils with a flash point between 55 °C and 75 °C may be regarded as Category 3 for some regulatory purposes.
The flash point is a test result
The flash point is the lowest liquid temperature at which, in a standard apparatus, the vapour above the liquid can be ignited by a test flame. Closed-cup methods (such as Pensky-Martens or Abel) give results a few degrees lower than open-cup methods; an explosion protection document uses the closed-cup value and states the method. For mixtures the value can vary from batch to batch.
“Not classified” does not mean no explosive atmosphere
CLP classification serves labelling in the supply chain, not hazardous area classification. An oil with a flash point above 60 °C can still form an explosive atmosphere when it is heated above its flash point (tank heating, a film on a hot surface), when it is sprayed, or when a pressurised leak forms a fine mist.
Where this classification sits in the explosion protection document
- Substance inventory. The classification on the safety data sheet is the first step in listing the flammable liquids on site.
- First filter. The real question is whether the liquid can form an explosive vapour at the most unfavourable process temperature. Flash point, process temperature and vapour pressure decide that together.
- Zoning is separate. The category does not give the type or extent of a zone; these follow from the release and ventilation assessment.
Sources
- Regulation (EC) No 1272/2008 (CLP), Annex I, section 2.6: Flammable liquids
- Turkish CLP regulation (SEA Yönetmeliği), Official Gazette 11.12.2013, No. 28848
This calculator is for information. The product's classification is given in the supplier's safety data sheet.
Frequently asked questions
If the flash point is above 60 °C, can there be no explosive atmosphere?
It can. If the liquid is heated above its flash point, sprayed, or can form a mist from a pressurised leak, an explosive atmosphere can occur. The decision depends on process temperature and release conditions and is justified in the document.
Why is the boiling point needed?
Only for liquids with a flash point below 23 °C: the initial boiling point separates Category 1 from Category 2. Liquids boiling at or below 35 °C (such as diethyl ether) are Category 1.
Why is there no Category 4 as in the GHS?
The UN GHS has a fourth category for liquids with a flash point between 60 °C and 93 °C. The European Union did not adopt it in CLP.