Where there are multiple boilers/furnaces which are individually below the Clean Air Act threshold of 366.4 kilowatts and are served by several chimneys, how should we check whether or not exceedances of the NO2 objective are likely?
The potential for exceedance of the objective may be assessed using the LAQM Industrial Emissions Screening Tool.
Alternatively, the table below provides aggregate thermal input rate screening limits for modular boiler installations with low NOx burners (<0.02g/MJ). Boiler installations with greater aggregate capacity than that given for a particular situation will require more detailed assessment. The table is based on the information provided in the Review of the Clean Air Act Provisions for Dispersion from Small Gas Boilers, linked below.
| Distance of Nearest Receptors (m) | 20 | 50 | 100 | 200 |
|---|---|---|---|---|
| Annual Background NO2 Concentration – 30µg/m3 |
0.6 | 2.1 | 5.7 | 16.6 |
| Annual Background NO2 Concentration – 32µg/m3 |
0.5 | 1.7 | 4.6 | 13.3 |
| Annual Background NO2 Concentration – 34µg/m3 |
0.4 | 1.3 | 3.4 | 10 |
| Annual Background NO2 Concentration – 36µg/m3 |
0.2 | 0.8 | 2.3 | 6.6 |
| Annual Background NO2 Concentration – 38µg/m3 |
— | 0.4 | 1.1 | 3.3 |
| Annual Background NO2 Concentration – 40µg/m3 |
— | 0.2 | 0.6 | 1.7 |
Documents
Review of the Clean Air Act Provisions for Dispersion from Small Gas Boilers
Released: September 2005 (PDF, 426KB, 37 pages)
Hosted on www.uk-air.defra.gov.uk
