NDIR Carbon Monoxide Analyzer

What is the NDIR Carbon Monoxide Analyzer?

A reference-grade analyzer that measures carbon monoxide in ambient air by non-dispersive infrared absorption. It is widely used in traffic-related, tunnel and urban air quality networks where CO serves as a key combustion marker.

Overview

The analyzer passes infrared light through a sample cell and measures absorption by carbon monoxide near 4.6 µm, using a broad-band source and a narrow bandpass filter rather than a dispersive element, hence the term non-dispersive. Gas filter correlation improves selectivity by comparing the signal through a cell filled with CO against a reference cell, subtracting the effect of interfering species such as water vapour and carbon dioxide. The measurement cell is heated above ambient to reduce condensation and temperature effects. Ranges of 0 to 50 ppm and 0 to 200 ppm are typical, with detection limits near 0.04 ppm and response times under 60 seconds. Internal computers apply zero and span correction, and readouts are available as 4 to 20 mA, serial and Ethernet. The instrument is robust and low maintenance, needing mainly filter and dryer replacement and periodic calibration with certified CO standards.

How does it work?

Ambient gas analyzers use a selective physical or chemical reaction to convert a gas concentration into an electrical signal. Sulfur dioxide is measured by ultraviolet fluorescence, where SO2 molecules excited at 214 nm emit light whose intensity is proportional to concentration. Nitrogen oxides are determined by chemiluminescence, reacting nitric oxide with ozone to produce light, with a molybdenum converter reducing NO2 to NO for the total. Carbon monoxide is measured by non-dispersive infrared absorption, often with gas filter correlation to reject interference. Ozone is determined by ultraviolet absorption at 254 nm in a dual-cell or single-cell design that alternates sample and scrubbed air. Sample conditioning removes particles and moisture, and internal computers apply zero and span corrections for temperature and pressure.

What are the key features?

• Non-dispersive infrared absorption detects CO at 4.6 µm with high stability.
• Gas filter correlation rejects water vapour and carbon dioxide interference.
• Heated measurement cell minimizes condensation and temperature drift.
• Wide range covers clean background and traffic-dominated concentrations.
• Automatic zero and span correction with stored drift records.
• Low maintenance design needs mainly filter and dryer service.

What are the technical specifications?

A typical ndir carbon monoxide analyzer configuration offers measurement principle of Non-dispersive infrared with gas filter correlation, absorption wavelength of 4.6 µm, measurement range of 0–50 ppm, 0–200 ppm selectable, lower detection limit of 0.04 ppm (2σ), response time of ≤ 60 s to 95% and zero drift of < 0.1 ppm per 24 h. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The NDIR Carbon Monoxide Analyzer is used in traffic-related urban CO monitoring, tunnel and underground car park air checks, industrial combustion source perimeter monitoring and indoor and occupational air quality studies. Across the wider Gas Analyzers class, laboratories also deploy it for urban air quality monitoring networks, industrial fence-line and plant perimeter monitoring and roadside and traffic-related pollution studies.

Which standards and certifications apply?

Relevant standards and methods include EN 14212 (SO2), EN 14211 (NOx), EN 14626 (CO), ISO 13964 (ozone), US EPA 40 CFR Part 50 Appendix A and HJ 654. Certification candidates for this model are CE, China environmental monitoring instrument certification and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Install analyzers in a temperature-controlled shelter or rack with clean, dry sample lines and a manifold that provides stable flow. Calibrate with certified gas standards and a dynamic dilution system, performing zero and span checks on the schedule required by the method, and keep records of converter efficiency for NOx instruments. Replace particulate filters, dryers and pump diaphragms regularly, and verify sample flow and pressure. Protect optical components from dust and condensation, and allow warm-up and stabilization before reporting data. For regulatory networks, follow quality assurance and quality control procedures such as US EPA 40 CFR Part 58 Appendix A and retain raw data for audit.

How do I select the right NDIR Carbon Monoxide Analyzer?

Select this analyzer for stable, low-maintenance CO reference data, especially where traffic sources dominate. Electrochemical CO sensors cost less and are portable but drift faster and need more frequent calibration. In an RFQ, specify the range, detection limit, method compliance and calibration gas supply.

How does it compare with other Gas Analyzers variants?

Choose the analyzer by the gas, the required measurement range and whether the data must satisfy a regulatory method. Reference-grade instruments follow EN or US EPA methods and provide the stability, detection limit and averaging time that monitoring networks require. Range should bracket the local concentrations and include the limit value, for example 0–500 ppb for SO2 and NOx in urban air or 0–50 ppm for CO near traffic. Consider interference rejection, response time, zero and span drift specifications and the calibration gas requirements. For indoor or occupational checks, portable or electrochemical analyzers with lower ranges and simpler calibration often suffice. Confirm output protocols, data logging and the availability of a multipoint calibration system.