How Does a Flue Gas Analyser Work?

How Does a Flue Gas Analyser Work?

Flue gas refers to the gas emissions that are generated through the combustion process and emitted through a building's chimney, known as a flue. The process of performing a flue gas analysis used to be a time consuming and expensive task. But thanks to modern advancement in technology, analysing flue gas is now cheaper and easier than ever.

But how does a flue gas analyser work?

How a flue gas analyser works

A flue gas analyser is used to measure the emissions of household appliances and monitor their safety. This is performed by determining how much harmful gas the appliances produce. Flue gas typically consists of the following:

  • Carbon dioxide
  • Nitrogen
  • Sulfur
  • Water vapour
  • Oxygen
  • Carbon monoxide
  • Solids (dust, soot)
  • A number of other pollutants

Of all of these emissions, the most harmful is carbon monoxide. Because it is colourless and odourless, it is difficult to detect without equipment and large amounts can kill someone quickly. A flue gas analyser can detect the risk  by testing the appliance or by monitoring the ambient air.

How to use a flue gas analyser

To monitor an appliance, the probe of the analyser needs to be placed in the exhaust of the appliance you are measuring. The sensor in the analyser will be able to detect gas emissions that the appliance emits. The results of this will be displayed on the digital screen, informing you of the risk of poisoning as well as the efficiency of the appliance

A similar process is used to monitor ambient  air as calculating a flue gas measurement, however you will instead conduct a combustion analysis in open air. A flue gas analyser is a useful measuring instrument for ensuring that all the air in a building is safe. Some gases, such as carbon monoxide, are deadly, so if a significant amount of these gasses are detected in open air it is a significant hazard.

What flue gas analyser readings should be

The desired readings of a flue gas analyser gas analyser may vary depending on which gas emissions you are measuring, as well as the appliance you are testing.

The CO/CO2 ratio, which is the amount of carbon monoxide in relation to the amount of carbon dioxide measured in the exit flue of an appliance, should be below 0.004 if running efficiently. Any level above that requires investigation, and anything over 0.008 is considered dangerous.

A carbon monoxide level below 100 parts per million (ppm) is considered safe, however anything above that is potentially dangerous. In addition to this, oxygen levels should not exceed 5% for gas appliances or 8% for oil appliances.

When measuring ambient levels of CO, a reading of less than 9ppm is considered good, while anything above 355ppm is dangerous and requires immediate action.

Types of flue gas analysers

Flue gas analysers used to be large, difficult-to-operate pieces of equipment. Thankfully that was decades ago. Today, flue gas analysers are portable. Testo’s products are lightweight, compact and easy to use and transport. The right flue gas analyser will depend entirely on your needs, mainly what type of generator you are inspecting. Testo can help you find the right one.
Different devices come with a variety of features. For instance, some gas analysers are specially designed with printers that enable users to quickly and easily create simple clear reports while on the work site.

If your main requirement is to take basic measurements on small-scale firing stations, then an affordable solution such as a Testo 310 Flue Gas Analyser Set will be more than sufficient.
Alternatively, anyone analysing large combustion plants, an industrial engine, a gas turbine or an industrial furnace, will need a top of the line emissions analyser such as the Testo 350 Multiple Sensor Gas Analysis System. 

If you are unsure which glue gas analyser is best for your needs, get in contact with the expert team at Testo New Zealand. We are more than happy to point you in the right direction.

How Testo can help

Testo are world leaders in portable and stationary measurement equipment and an authority on flue gas and flue gas analysis.
Testo New Zealand stocks a wide variety of devices designed to measure, analyse and document flue gas and determine whether combustion systems are operating safely and efficiently. For more information on flue gas analysers, get in contact with the team at Testo New Zealand today!