Know More about Flammability Range

Flammability range is the concentration range in which gas or vapor of combustibles or fuels to normal air, on specific pressure and temperature, can produce flame propagation in the presence of an ignition source. The flammability range has a lower and upper limit which are presented in volume percent.

Lower Flammability Limit (LFL) dan Upper Flammability Limit (UFL)

LFL and UFL are the lower and lower limit of the flammability range, respectively. Table 1 shows the LFL and UFL of various fuel gases at atmospheric pressure and 20oC temperature.

Table 1. List of LFL and UFL of various fuel gases at atmospheric pressure and 25oC temperature*.

Fuel Gas

LFL 

(% by air volume)

UFL 

(% by air volume)

Acetaldehyde

4

60

Acetic acid

4

19.9

Acetone

2.6

12.8

Acetonitrile

3

16

Acetyl chloride

7.3

19

Acetylene

2.5

100

Acrolein

2.8

31

Acrylic acid

2.4

8

Acrylonitrile

3.0

17

Allyl chloride

2.9

11.1

Allyll alcohol

2.5

18

Alyllamine

2.2

22

Ammonia

15

28

Aniline

1.3

11

Arsine

5.1

78

Benzene

1.2

7.8

Biphenyl

0.6

5.8

Bromobuthane (1-Bromobuthane)

2.6

6.6

Bromoethane

6.8

8

Bromoethene

9

15

Butadiene (1,3-Butadiene)

2.0

12

Butanal

1.9

12.5

Butane (n-Butane)

1.86

8.41

Butanoic acid

2

10

Butyl acetate

1.7

7.6

Butyl alcohol, Butanol

1

11

Butyl formate

1.7

8.2

Butyl methyl ketone

1

8

Butylamine

1.7

9.8

Butylbenzene

0.5

5.8

Butylene

1.98

9.65

Butyll acrylate

1.9

9.9

Carbon disulfide

1.3

50

Carbon monoxide

12

75

Carbon oxysulfide

12

29

Chlorobenzene

1.3

9.6

Chloroethane

3.8

15.4

Cyanogen

6.0

42.6

Cyclobutane

1.8

11.1

Cycloheptane

1.1

6.7

Cyclohexane

1.3

8

Cyclohexanol

1

9

Cyclohexanone

1

9

Cyclopropane

2.4

10.4

Decane

0.8

5.4

Diacetone alcohol

1.8

6.9

Diborane

0.8

88

Dibutylamine

1.1

6

Dichloroethane (1,1-Dichloroethane)

6

11

Diesel fuel

0.6

7.5

Diethanolamine

2

13

Diethyl ether

1.9

36

Diethylamine

2

13

Diethylether

1.9

48

Diisobutyl ketone

1

6

Diisopropyl ether

1

21

Dimethyl sulphoxide

3

42

Epichlorohydrin

4

21

Ethane

3

12.4

Ethyl acetate

2

12

Ethyl acrylate

1.4

14

Ethyl alcohol, Ethanol

3.3

19

Ethyl chloride

3.8

15.4

Ethyl nitrite

4

50

Ethyl propyl ether

1.7

9

Ethyl vinyl ether

1.7

28

Ethylamine

3.5

14

Ethylbenzene

1.0

7.1

Ethylcyclobutane

1.2

7.7

Ethylene

2.75

28.6

Ethylene oxide

3

100

Etylene glycol

3

22

Fluoroethene

2.6

21.7

Formaldehyde

7

73

Formic acid

18

57

Fuel Oil - No.1

0.7

5

Furan

2

14

Furfural

2

19

Gasoline

1.4

7.6

Glycerol

3

19

Heptane

1.0

6.7

Heptane (n-Heptane)

1.0

6.0

Hexane

1.1

7.5

Hexane (n-Hexane)

1.25

7.0

Hydrazine

5

100

Hydrogen

4

75

Hydrogen

6

40

Hydrogen sulfide

4.3

46

Isobutanal

1.6

10.6

Isobutane

1.80

8.44

Isobutene

1.8

9.0

Isobutyl alcohol

2

11

Isooctane

0.79

5.94

Isopentane

1.32

9.16

Isophorone

1

4

Isopropyl alcohol, Isopropanol

2

12

Isopropylbenzene

0.9

6.5

Kerosene Jet A-1

0.7

5

Mesityl oxide

1.4

7.2

Methacrylic acid

1.6

8.8

Methane

4.4

16.4

Methylamine

4.9

20.7

Methyl acetate

3

16

Methyl alcohol, Methanol

6.7

36

Methyl acrylate

2.8

25

Methyl chloride

10.7

17.4

Methyl ethyl Ketone

1.8

10

Methyl formate

4.5

23

Methylhydrazine

2.5

92

Methyl isocyanate

5.3

26

Mineral spirits

0.7

6.5

Naphtalene

0.9

5.9

Naphthalene

0.9

5.9

Neohexane

1.19

7.58

Neopentane

1.38

7.22

Nitrobenzene

2

9

Nitroethane

3.4

17

Nitromethane

7.3

22.2

Nonane

0.8

2.9

Octane (n-Octane)

1.0

7

Oxirane

3

100

Paraformaldehyde

7

73

Pentane (n-Pentane)

1.4

7.8

Pentene (n-Pentene)

1.65

7.7

Pentyl acetat

1.1

7.5

Pentylamine

2.2

22

Phenol

1.8

8.6

Piperidine

1

10

Propane

2.1

10.1

Propanoic acid

2.9

12.1

Propene

2

11.1

Propyl acetate

2

8

Propylamine

2

10.4

Propylbenzene

0.8

6

Propyl nitrate

2

100

Propylene

2.0

11.1

Propylene oxide

2.3

36

Propyne

2.1

12.5

Pyridine

2

12

Silane

1.5

98

Styrene

1.1

6.1

Tetrafluoroethene

10

50

Tetrahydrofuran

2

12

Toluene

1.1

7.1

Trichloroethylene

13

90

Triethylene glycol

0.9

9.2

Triptane

1.08

6.69

Trimethylamine

2

11.6

Turpentine

0.8


Vinyl acetate

2.6

13.4

Vinyl butanoate

1.4

8.8

Vinyl chloride

3.6

33

o-Xylene

0.9

6.7

m-Xylene

1.1

7

p-Xylene

1.1

7

*) Source: https://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html 

To help us understand what LFL and UFL are, let us take a look at fires due to gas leakage, particularly, liquified petroleum gas (LPG).

According to the Directorate General of Oil and Gas of Indonesia, LPG is classified into three types. The types are based on LPG’s main components. Those types are LPG propane, LPG butane, and LPG mix (a combination of propane and butane). Let us use LPG propane as an example. 

When there is no leakage, the kitchen is full of air. Once the gas leaks, propane starts to fill the kitchen. At some point, the volume of propane will reach 2.1% of the air volume. As long as the concentration of the mixture between propane and air in the atmosphere lies within the flammability range, the atmosphere in the kitchen is considered flammable. A small ignition source (e.g., turning the stove on) can lead to flame propagation and causes a fire (or even an explosion). Thus, it is important to have good ventilation in a room where gases are stored or used. 

Effect of Temperature and Pressure on Flammability Range

As stated above, the LFL and UFL in Table 1 are for gases under atmospheric pressure and 20oC temperature. Why is this information important? In fact, with different pressure and temperature, the LFL and UFL will be different. Increasing temperature and pressure will widen the gap between LFL and UFL (LFL shifts to lower concentrations and UFL to higher concentrations). Hence, the gas mixture will be easier to catch fire or, even worse, explode.


Written by

Fitri Endrasari

source : https://migas.esdm.go.id/post/read/Mengenal-Jenis-jenis-Gas-Bumi


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