Calculators · Performance Toolkit
Excess Air from O₂
Converts a flue gas O₂ reading to excess air percentage and stoichiometric air ratio (λ). Use alongside a CO check — low O₂ alone does not confirm safe combustion.
Inputs
Fuel Type
Affects O₂ correction for wet/dry basis. EA formula is identical across fuels at this level of approximation.
Flue Gas O₂
%
Typical target range: 2 – 4 % (dry). Above 6 % indicates high excess air.
Enter a value between 0.1 and 15 %
O₂ Measurement Basis
Portable analysers typically measure dry. Confirm with instrument datasheet.
CO Risk at Low O₂
Excess air below ~5% is high-risk territory for CO breakthrough, especially with fluctuating fuel composition or poor air distribution. Always verify CO alongside O₂.
Results
Enter O₂ % and press
Calculate to see results
Calculate to see results
O₂ → Excess Air Quick Reference
| O₂ % (dry) | Excess Air % | λ | Zone |
|---|
Calculation method:
Excess air is calculated as
EA% = (O₂_dry × 100) / (20.9 − O₂_dry),
where 20.9 % is the O₂ fraction in atmospheric air.
The air factor λ = 1 + EA/100.
Wet O₂ is converted to dry using an approximate factor of 1.07
.
The formula is fuel-type independent at this level of approximation
.
⚠ Results are indicative only, based on a simplified formula. Not suitable for engineering design, regulatory submissions, or safety-critical decisions. A low EA reading does not confirm safe combustion — always check CO and flame condition.
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