Combustion Gas Composition Calculator

Combustion Gas Composition Calculator: Find N2 by Difference

Classic gas analysis instruments like the Orsat apparatus directly measure CO2, O2, and CO, but nitrogen (plus trace argon) is almost always found by difference since it makes up the bulk of the remaining volume and is difficult to measure directly by absorption methods. This calculator applies that standard approach.

The Formula

N2% = 100 − CO2% − O2% − CO%

Worked Example

A gas analysis shows 12% CO2, 5% O2, and 0.5% CO.

N2% = 100 − 12 − 5 − 0.5 = 82.5%

How to Use This Calculator

1. Enter the measured CO2 percentage by volume.
2. Enter the measured O2 percentage by volume.
3. Optionally enter the measured CO percentage if incomplete combustion is present.
4. Click Calculate to get the nitrogen percentage by difference.

Related Calculations

Cross-check with the Flue Gas Nitrogen Calculator and Flue Gas CO2 Calculator.