How do I calculate NOx, SOx and PM for the BRSR air emissions table?
Use your stack monitoring reports. For each stack, multiply the measured concentration in mg/Nm3 by the flue gas flow in Nm3/h and the operating hours, then divide by 10^9 to get tonnes. Add all stacks. Where a stack has no monitoring, estimate SOx from fuel sulphur and say so.
What the BRSR table asks for
Principle 6 of the BRSR format has an essential indicator on air emissions other than greenhouse gases: NOx, SOx, particulate matter, persistent organic pollutants, volatile organic compounds, hazardous air pollutants and others, each with a unit, for the current and previous year. It also asks whether an external agency assessed the figures. Report what you measure; write not applicable only for pollutants your processes do not emit.
Where the numbers come from
- Stack monitoring reports from a laboratory recognised under the Environment (Protection) Act, required by your consent to operate under the Air (Prevention and Control of Pollution) Act 1981.
- Continuous emission monitoring data, if your sector must run online monitoring for the CPCB.
- Operating hours per stack from the boiler, furnace or DG logbook.
- Fuel quantity and sulphur content, for a mass balance where no monitoring exists.
Calculating from monitoring data
- For each stack and pollutant, take the average concentration across the year's reports.
- Use flow and concentration on the same basis. Reports often correct concentration to a reference oxygen level; do not combine a corrected concentration with an uncorrected flow.
- Tonnes = mg/Nm3 x Nm3/h x hours / 1,000,000,000.
- Sum the stacks, including DG sets, and keep the calculation sheet with the reports.
Estimating SOx from fuel when there is no stack data
Sulphur burns to SO2, which weighs twice the sulphur. SO2 in kg = fuel burnt in kg x sulphur fraction x 2, assuming all sulphur leaves the stack. Take sulphur content from the fuel supplier's test certificate. Label the figure as calculated, not measured.
Worked example: one boiler stack and a fuel-based SOx check
- PM: 150 mg/Nm3 x 20,000 Nm3/h x 6,000 h = 18,000,000,000 mg; / 10^9 = 18 t a year
- NOx on the same stack at 300 mg/Nm3: 300 x 20,000 x 6,000 / 10^9 = 36 t
- SOx by mass balance: furnace oil 5,00,000 kg at an assumed 3.5% sulphur
- 5,00,000 x 0.035 x 2 = 35,000 kg SO2, 35 t, labelled calculated
Concentrations and sulphur content are illustrative. Use your monitoring reports and fuel certificates.
What Senseible does here
Senseible reads fuel invoices and keeps the fuel quantities, which are the starting point for a sulphur mass balance. NOx, SOx and PM figures for BRSR come from your stack monitoring reports; Senseible's own calculations cover greenhouse gases.
Sources: SEBI BRSR format (July 2023), Principle 6, CPCB emission standards and stack monitoring under the Air (Prevention and Control of Pollution) Act, 1981
Last reviewed 2026-10-17.