Air: 1.66
Con: 15-30

For New Curve (R² >= 0.9995):

for ppm = a*ratio^b:

Gas    | a       | b
Ethanol| 3.3559  | -0.3563
Hydrogen| 3.6812  | -0.4308
Methane| 7.3489  | -0.5979
Iso-Butane| 2.7521  | -0.4732

for ppm = 10^[(log10(ratio)-b)/m]:

Gas    | m       | b
Ethanol| -0.3563 | 0.5258 
Hydrogen| -0.4308 | 0.566  
Methane| -0.5979 | 0.8662 
Iso-Butane| -0.4732 | 0.4397 


For Old Curve:

for ppm = a*ratio^b:

Gas    | a       | b
Ethanol| 3.3559  | -0.3563
Hydrogen| 3.6812  | -0.4308
Methane| 7.3489  | -0.5979
Iso-Butane| 2.7521  | -0.4732

for ppm = 10^[(log10(ratio)-b)/m]:

Gas    | m       | b
Ethanol| -0.3563 | 0.5258 
Hydrogen| -0.4308 | 0.566  
Methane| -0.5979 | 0.8662 
Iso-Butane| -0.4732 | 0.4397 


Ethanol
100, 0.65
300, 0.44
1000, 0.29
3000, 0.19

%17.46
[(100, 0.65), (300, 0.44), (1000, 0.29), (3000, 0.19)]

Hydrogen
100, 0.51
300, 0.31
1000, 0.18
3000, 0.12
10000, 0.082

%10.84
[(100, 0.51), (300, 0.31), (1000, 0.18), (3000, 0.12), (10000, 0.082)]

Methane
100, 0.47
300, 0.24
1000, 0.11
3000, 0.068
10000, 0.041

%6.63
[(100, 0.47), (300, 0.24), (1000, 0.11), (3000, 0.068), (10000, 0.041)]

Iso-butane
100, 0.31
300, 0.19
1000, 0.1
3000, 0.06
10000, 0.039

%6.02
[(100, 0.31), (300, 0.19), (1000, 0.1), (3000, 0.06), (10000, 0.039)]
