Ambient Concentration Estimate Calculator

Work out ambient concentration estimate instantly with clear inputs, formula shown and shareable results.

About Ambient Concentration Estimate Calculator

Predicted environmental concentration is the process contribution, from emission rate times a dispersion factor, added to the existing background. Screening criteria commonly treat a process contribution below 1% of the long-term standard as insignificant, and compliance is judged on the total against the standard.

Formulas

Predicted concentration

Total = background + emission rate x dispersion factor

Significance

Process contribution as a percentage of the air quality standard

Worked example

With the default values below, Ambient Concentration Estimate Calculator returns Total Predicted Concentration of 10,012.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Emission Mass Rateminimum 0 g/s: 25 g/s
Dispersion Factorminimum 0 microg/m3 per g/s: 0.0004 microg/m3 per g/s
Background Concentrationminimum 0 microg/m3: 12 microg/m3
Air Quality Standardminimum 0 microg/m3: 40 microg/m3

Results

Total Predicted Concentration: 10,012.0000
Process Contribution: 10,000.0000
Percentage Of Standard: 25,030.000%
Compliance Assessment: Exceeds air quality standard

Step by step

1Values used
2Predicted concentration
3Significance
4Total Predicted Concentration= 10,012.0000
5Process Contribution= 10,000.0000
6Percentage Of Standard= 25,030.000
7Compliance Assessment= Exceeds air quality standard

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Air quality assessment for permitting must follow the regulator's approved methodology with site-specific modelling and monitored background data.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Air quality assessment for permitting must follow the regulator's approved methodology with site-specific modelling and monitored background data.

Frequently Asked Questions

Why must background be included?

Because the standard applies to the total concentration a person breathes. A small process contribution can still cause exceedance where background is already close to the limit.

Where does the dispersion factor come from?

From a dispersion model run for the site, or from a generic screening factor. Site-specific modelling with local meteorology is required for permit determinations.