Table
37 substances.
| Substance | LEL % | UEL % | 1 LEL (ppm) | Flash point °C | AIT °C | T class | Gas group | Density (air = 1) | Source |
|---|---|---|---|---|---|---|---|---|---|
| MethaneCAS 74-82-8 | 4.4 | 17 | 44,000 | gas | 595 | T1 | IIA | 0.55 (lighter) | a |
| EthaneCAS 74-84-0 | 2.4 | 15.5 | 24,000 | gas | 515 | T1 | IIA | 1.04 (close to air) | b |
| PropaneCAS 74-98-6 | 1.7 | 10.8 | 17,000 | gas | 450 | T2 | IIA | 1.52 (heavier) | a |
| n-ButaneCAS 106-97-8 | 1.4 | 9.3 | 14,000 | gas | 372 | T2 | IIA | 2.01 (heavier) | b |
| IsobutaneCAS 75-28-5 | 1.3 | 9.8 | 13,000 | gas | 460 | T1 | IIA | 2.01 (heavier) | b |
| EthyleneCAS 74-85-1 | 2.3 | 36 | 23,000 | gas | 440 | T2 | IIB | 0.97 (close to air) | b |
| PropyleneCAS 115-07-1 | 2 | 11.1 | 20,000 | gas | 455 | T1 | – | 1.45 (heavier) | b |
| AcetyleneCAS 74-86-2 | 2.3 | 100 | 23,000 | gas | 305 | T2 | IIC | 0.90 (lighter) | b |
| HydrogenCAS 1333-74-0 | 4 | 77 | 40,000 | gas | 500 | T1 | IIC | 0.07 (lighter) | a |
| AmmoniaCAS 7664-41-7 | 14 | 33.6 | 140,000 | gas | 630 | T1 | IIA | 0.59 (lighter) | a |
| Carbon monoxideCAS 630-08-0 | 10.9 | 74 | 109,000 | gas | 607 | T1 | – | 0.97 (close to air) | b |
| Ethylene oxideCAS 75-21-8 | 2.6 | 100 | 26,000 | gas | 429 | T2 | IIB | 1.52 (heavier) | b |
| AcetoneCAS 67-64-1 | 2.5 | 14.3 | 25,000 | −20 | 465 | T1 | IIA | 2.01 (heavier) | a |
| EthanolCAS 64-17-5 | 3.1 | 27.7 | 31,000 | 12 | 363 | T2 | IIB | 1.59 (heavier) | a |
| MethanolCAS 67-56-1 | 6 | 50 | 60,000 | 9 | 440 | T2 | IIA | 1.11 (heavier) | a |
| IsopropanolCAS 67-63-0 | 2 | 12.7 | 20,000 | 12 | 399 | T2 | – | 2.07 (heavier) | b |
| n-ButanolCAS 71-36-3 | 1.4 | 12 | 14,000 | 35 | 343 | T2 | – | 2.56 (heavier) | b |
| TolueneCAS 108-88-3 | 1 | 7.8 | 10,000 | 4 | 480 | T1 | IIA | 3.18 (heavier) | a |
| o-XyleneCAS 95-47-6 | 1 | 7.6 | 10,000 | 30 | 470 | T1 | – | 3.67 (heavier) | b |
| m-XyleneCAS 108-38-3 | 1 | 7 | 10,000 | 25 | 465 | T1 | – | 3.67 (heavier) | b |
| p-XyleneCAS 106-42-3 | 0.9 | 7.6 | 9,000 | 25 | 535 | T1 | – | 3.67 (heavier) | b |
| BenzeneCAS 71-43-2 | 1.2 | 8.6 | 12,000 | −11 | 498 | T1 | IIA | 2.70 (heavier) | b |
| n-PentaneCAS 109-66-0 | 1.1 | 8.7 | 11,000 | −40 | 243 | T3 | IIA | 2.49 (heavier) | b |
| n-HexaneCAS 110-54-3 | 1 | 8.9 | 10,000 | −26 | 225 | T3 | IIA | 2.98 (heavier) | a |
| n-HeptaneCAS 142-82-5 | 0.85 | 6.7 | 8,500 | −7 | 204 | T3 | IIA | 3.46 (heavier) | b |
| CyclohexaneCAS 110-82-7 | 1 | 8 | 10,000 | −17 | 244 | T3 | – | 2.91 (heavier) | b |
| Ethyl acetateCAS 141-78-6 | 2 | 12.8 | 20,000 | −4 | 427 | T2 | IIA | 3.04 (heavier) | a |
| Methyl acetateCAS 79-20-9 | 3.1 | 16 | 31,000 | −10 | 505 | T1 | – | 2.56 (heavier) | b |
| n-Butyl acetateCAS 123-86-4 | 1.2 | 8.5 | 12,000 | 22 | 390 | T2 | – | 4.01 (heavier) | b |
| Diethyl etherCAS 60-29-7 | 1.7 | 48 | 17,000 | −45 | 160 | T4 | IIB | 2.56 (heavier) | a |
| Tetrahydrofuran (THF)CAS 109-99-9 | 1.5 | 12.4 | 15,000 | −14 | 230 | T3 | – | 2.49 (heavier) | b |
| AcetaldehydeCAS 75-07-0 | 4 | 60 | 40,000 | −38 | 155 | T4 | – | 1.52 (heavier) | b |
| Acetic acidCAS 64-19-7 | 4 | 19.9 | 40,000 | 39 | 510 | T1 | – | 2.07 (heavier) | b |
| Dimethylformamide (DMF)CAS 68-12-2 | 1.8 | 16 | 18,000 | 58 | 440 | T2 | – | 2.52 (heavier) | b |
| StyreneCAS 100-42-5 | 1 | 8 | 10,000 | 30 | 490 | T1 | – | 3.60 (heavier) | b |
| Carbon disulphideCAS 75-15-0 | 0.6 | 60 | 6,000 | −30 | 90 | T6 | IIC | 2.63 (heavier) | a |
| Diesel fuelmixture | SDS | SDS | – | > 55 | 220 | T3 | IIA | – | a |
Source a: compilation of GESTIS, NIOSH and ISO/IEC 80079-20-1 data; the conservative end of the range between sources (lowest LEL and AIT, highest UEL). Source b: IEC 60079-20-1:2010 data table; where the gas group is blank, that table does not give one. The minimum flash point of diesel comes from EN 590; take its explosive limits from the product's SDS. To convert a value to ppm, g/m³ or %LEL, use the LEL calculator.
What the columns mean
- LEL and UEL. Lower and upper explosive limits: between these two concentrations in air the substance can ignite. Given in % by volume.
- 1 LEL (ppm). The lower explosive limit in ppm (LEL × 10,000). Useful to compare a detector's %LEL reading with ppm values in a measurement report.
- Flash point. The lowest liquid temperature at which the vapour above it can be ignited by a test flame. If the liquid is handled above this temperature, an explosive vapour can form.
- AIT and T class. Autoignition temperature. The maximum surface temperature of equipment in the zone must stay below it. The T class in the table is the minimum class the equipment needs: where it says T3, T3, T4, T5 and T6 are suitable.
- Gas group. IIA, IIB or IIC. IIC is the most demanding group; IIC equipment may be used for all gas groups, IIA equipment only for IIA substances.
- Density. Density relative to air (molar mass / 28.96). Above 1 the vapour sinks and can collect in pits, trenches and drains.
Why values differ between sources
Explosive limits and autoignition temperatures are test results: they change with the apparatus, the temperature and the pressure. Sources therefore often give a range; the lower explosive limit of methane, for example, is 4.4 % to 5.0 % depending on the source. An explosion protection document uses the conservative value and states the source.
If the safety data sheet (section 9) gives a different value, especially for a mixture, that value applies.
Where this table sits in the explosion protection document
- Substance properties. The first step of the document is to record these values, with their source, for every flammable substance on site.
- Equipment selection. The T class and the gas group decide whether Ex equipment in the zone is suitable. The Ex equipment check compares them for you.
- Dispersion. Vapours heavier than air can collect in low points; the document assesses these points separately.
The table does not decide zones. The type and extent of a zone are calculated from where, how often and how much is released, and from the ventilation.
Sources
- GESTIS substance database (IFA, Germany)
- NIOSH (USA)
- ISO/IEC 80079-20-1 (classification data for gases and vapours) and its predecessor IEC 60079-20-1:2010
- EN 590 (diesel fuel)
This table is for information. For the substance on your site, the current safety data sheet and the relevant standards apply.
Frequently asked questions
What is the difference between LEL and UEL?
LEL is the lower and UEL the upper explosive limit. Below the LEL the mixture is too lean to ignite, above the UEL too rich; between them lies the explosive range. A leak reaches the LEL first, so safety work usually relies on the LEL.
What does heavier than air mean?
A gas or vapour with a relative density above 1 is heavier than air: it does not rise but sinks and collects in low places. Propane, butane and most solvent vapours behave like this. Hydrogen, methane and ammonia are lighter than air.
The table says T3. Can I use T4 equipment?
Yes. The higher the class number, the lower the permitted surface temperature: T4 equipment may reach 135 °C, T3 equipment 200 °C. Where T3 is required, T3, T4, T5 and T6 are suitable.
My substance is not in the table. What now?
Look at section 9 of the product's safety data sheet: explosive limits, flash point and autoignition temperature are listed there. The GESTIS database also gives data for many substances free of charge. For mixtures the values depend on the composition; the supplier's data apply.