🌿 Carbon monoxide (CO) in waste gases — NDIR (reference method)
In short
Continuous measurement of the concentration of carbon monoxide in waste gases with an infrared absorption analyser (NDIR, e. The test is performed according to PN-EN 15058:2017-04 (EN 15058:2017); Range of validation: 0–400 mg/m³ (large combustion plants), 0–740 mg/m³ (incineration plants); sampling 30 min. The procedure comprises 5 steps; it is used for: Periodic measurements of CO emissions from boilers, waste incineration and co-incineration plants, industrial furnaces, engines and turbines, Calibration and control (QAL2, AST) of automated CO analysers — the reference method under the regulation on measurements of emissions, Assessment of the completeness of combustion and of the operation of the burners.
At a glance
- Standard: PN-EN 15058:2017-04 (EN 15058:2017)
- Category: Environment
- Procedure steps: 5
- Range of validation: 0–400 mg/m³ (large combustion plants), 0–740 mg/m³ (incineration plants); sampling 30 min
- Result: mg/m³ CO, dry gas, 273 K, 101.3 kPa, reference O₂
- IR interferences: water vapour, CO₂, N₂O, hydrocarbons — suppressed by the design of the analyser (e.g. gas filter correlation)
Overview
EN 15058 specifies the standard reference method (SRM) based on infrared (IR) absorption for the determination of carbon monoxide in waste gases from ducts and stacks; it covers the gas sampling and conditioning system and the analyser. The standard gives the characteristics and the criteria for IR measuring systems, it is applied to periodic monitoring and to the calibration and control of automated measuring systems (AMS), and it lays down criteria for the equivalence of alternative methods (EN 14793). It was validated in field tests at incineration plants, co-incineration plants and large combustion plants and on a test rig for sampling periods of 30 min in the range 0–400 mg/m³ CO (large combustion plants) and 0–740 mg/m³ (incineration and co-incineration plants); Directive 2010/75/EU expresses the limit values in mg/m³ for dry gas at a specified oxygen content at 273 K and 101.3 kPa. The 2017 edition replaced EN 15058:2006. In Poland the regulation on the measurement of the quantity of emissions indicates PN-EN 15058 as the reference method for CO in the control of continuous measurements.
Method principle
The attenuation of the infrared radiation passing through the measuring cell is a measure of the concentration of CO in accordance with the Lambert–Beer law. IR radiation is absorbed also by other heteroatomic molecules — water and CO₂ in particular have broad bands interfering with the measurement of CO — and for that reason solutions suppressing the cross-sensitivity are used. In the non-dispersive method (NDIR) the concentration is measured electro-optically through the absorption of a specified wavelength: the IR light is directed through the measuring chamber to the detector, in parallel a reference chamber with an enclosed gas (usually nitrogen) is in operation, and an optical filter in front of the detector transmits only the wavelength absorbed by CO; techniques such as gas filter correlation limit the cross-sensitivity, the instability and the drift. Particular attention is required for the gases absorbing IR: water vapour, carbon dioxide, dinitrogen monoxide and hydrocarbons. The analyser is connected to an extractive sampling system (probe, filter, line, conditioning) in one of the configurations: a condensation cooler, a permeation dryer, dilution with dry air or nitrogen, or a heated line to a heated analyser. The concentration is measured in volume units (with calibration with a volumetric standard) and expressed in mg/m³ by means of standard conversion factors.
Applications
- Periodic measurements of CO emissions from boilers, waste incineration and co-incineration plants, industrial furnaces, engines and turbines
- Calibration and control (QAL2, AST) of automated CO analysers — the reference method under the regulation on measurements of emissions
- Assessment of the completeness of combustion and of the operation of the burners
- Demonstration of the equivalence of alternative methods (e.g. electrochemical) with respect to the SRM
- Measurements during the commissioning and the optimisation of combustion installations
Key parameters
| Parameter | Value |
|---|---|
| Range of validation | 0–400 mg/m³ (large combustion plants), 0–740 mg/m³ (incineration plants); sampling 30 min |
| Result | mg/m³ CO, dry gas, 273 K, 101.3 kPa, reference O₂ |
| IR interferences | water vapour, CO₂, N₂O, hydrocarbons — suppressed by the design of the analyser (e.g. gas filter correlation) |
| Conditioning | a cooler, a permeation dryer, dilution or a heated line |
| Span gas | usually about 80 % of the upper limit of the range |
| Uncertainty | expanded, from the uncertainty budget, k = 2 (95 %) |
Standard
- Standard number
- PN-EN 15058:2017-04 (EN 15058:2017)
- Title (PL)
- Emisja ze źródeł stacjonarnych — Oznaczanie stężenia masowego tlenku węgla — Standardowa metoda odniesienia: spektrometria niedyspersyjna w podczerwieni
- Title (EN)
- Stationary source emissions — Determination of mass concentration of carbon monoxide — Standard reference method: non-dispersive infrared spectrometry
Step-by-step procedure
-
Planning
Plan the measurement in accordance with EN 15259; establish the expected concentrations of CO and CO₂ and the humidity, choose the range of the analyser and the configuration of the conditioning.
-
Assembly
Install the probe, the filter, the line and the conditioning; heat the parts, check the leak-tightness.
-
Adjustment
Feed zero gas and span gas directly and through the probe; check the response time, the linearity and the influence of the interferents (CO₂, H₂O) in accordance with the requirements of the standard.
-
Measurement
Record the concentration of CO continuously over the averaging period (e.g. 30 min); measure the O₂ and the humidity in parallel for the conversions.
-
Drift check and calculations
After the measurement check the zero and the span; convert the volume concentrations to mg/m³ (clause 10 of the standard), to dry gas under standard conditions and to reference O₂; draw up an uncertainty budget.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| NDIR CO analyser | with a measuring chamber and a reference chamber (nitrogen), an optical filter; e.g. the gas filter correlation technique | — |
| Sampling probe with a particulate filter | inert materials, heated above the dew point | — |
| Sampling line and conditioning system | a cooler, a permeation dryer, a dilution system or a heated line | — |
| Test gases: zero (N₂) and span (CO in N₂) | span concentration about 80 % of the range | — |
| Data recording system | continuous recording of the readings | — |
Health and safety (OHS)
- The carbon monoxide in the test gases and in the sample is poisonous — discharge the outlet of the analyser to the outside, the room ventilated, a CO detector
- The heated parts of the sampling system and work on the stack platform — heat-resistant gloves, protection against falling
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 15058:2017-04 (EN 15058:2017) — “Stationary source emissions — Determination of mass concentration of carbon monoxide — Standard reference method: non-dispersive infrared spectrometry”.
How does this method work?
The attenuation of the infrared radiation passing through the measuring cell is a measure of the concentration of CO in accordance with the Lambert–Beer law. IR radiation is absorbed also by other heteroatomic molecules — water and CO₂ in particular have broad bands interfering with the measurement of CO — and for that reason solutions suppressing the cross-sensitivity are used.
What is the measuring range and accuracy?
Range of validation: 0–400 mg/m³ (large combustion plants), 0–740 mg/m³ (incineration plants); sampling 30 min; Result: mg/m³ CO, dry gas, 273 K, 101.3 kPa, reference O₂; IR interferences: water vapour, CO₂, N₂O, hydrocarbons — suppressed by the design of the analyser (e.g. gas filter correlation); Conditioning: a cooler, a permeation dryer, dilution or a heated line.
How long does the test take?
The procedure comprises 5 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
NDIR CO analyser, Sampling probe with a particulate filter, Sampling line and conditioning system, Test gases: zero (N₂) and span (CO in N₂), Data recording system.
Where is this test used?
Periodic measurements of CO emissions from boilers, waste incineration and co-incineration plants, industrial furnaces, engines and turbines; Calibration and control (QAL2, AST) of automated CO analysers — the reference method under the regulation on measurements of emissions; Assessment of the completeness of combustion and of the operation of the burners; Demonstration of the equivalence of alternative methods (e.g. electrochemical) with respect to the SRM; Measurements during the commissioning and the optimisation of combustion installations.
What safety precautions apply?
The carbon monoxide in the test gases and in the sample is poisonous — discharge the outlet of the analyser to the outside, the room ventilated, a CO detector; The heated parts of the sampling system and work on the stack platform — heat-resistant gloves, protection against falling.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 15058.