What is Flue Gas Analysis?

A flue gas analysis measures the types and levels of gases appliances give off. They should be performed after installing any appliance that generates heat, filters or creates gas. By regularly testing flue gases, you can help customers fine-tune their heating appliances so fuel is used efficiently—saving energy and cutting down on their running costs. Plus, checking gas levels can literally be a lifesaver — catching dangerous levels of gases like carbon monoxide before they put anyone at risk.

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1. What is the purpose of a flue gas analysis?
2. When do you need to perform a flue gas analysis?
3. A step-by-step guide for performing a flue gas analysis

1. What is the purpose of a flue gas analysis?

Unless there's a huge concentration of particularly smelling gas lingering around, it's unlikely you or your customers would notice without accurate testing — until bigger problems occur. A flue gas analysis reveals problems, including blocked flues, incorrect air-to-fuel ratios, poor venting, safety risks, and expensive energy inefficiencies.

By analysing the levels of oxygen (O₂), carbon monoxide (CO), and carbon dioxide (CO₂), tradespeople can see how effectively a system burns fuel or if a blockage has occurred. If a boiler isn’t burning fuel efficiently, it may lead to higher energy bills, increased wear and tear on equipment, or dangerous carbon monoxide buildup. If something is blocked or jammed the flues, dangerous gases like carbon monoxide (CO) can back up into the customer's home. 

2. When do you need to perform a flue gas analysis?

Anyone working in HVAC or plumbing should be comfortable performing a flue gas analysis. Ideally, you'd perform a flue gas analysis when:

• Installing a new heating appliance

  • So, you’ve installed a brand-new boiler, and so far it’s running like a dream. To check that it'll stay that way, a flue gas analysis ensures that the boiler (or furnace) operates within the manufacturer’s specs and burns fuel like it’s supposed to.
    
    

• Routine maintenance and servicing

  • Systems age, and not always gracefully. Flue gas analysis helps catch issues before they snowball into bigger (and more expensive) problems, like carbon monoxide leaks or poor combustion. 
    
    

• Diagnosing performance issues

  • Customer calls about weird smells, uneven heating, or increasing fuel bills? Whip out the analyser. It can pinpoint culprits like incomplete combustion, blocked flues, or a funky air-to-fuel ratio faster than you can say “problem solved.”
    
    

• Safety inspections

  • Carbon monoxide doesn’t mess around, and neither should you. Flue gas analysis checks for harmful gases and makes sure your customer’s home isn’t turning into a gas-filled danger zone. If you can’t vent it, don’t install it!
    
    

• Energy efficiency audits

  • Want to be the hero who saves your customers money? Use flue gas analysis to recommend upgrades or tweaks that improve system efficiency, lower fuel costs, and keep that carbon footprint in check. You’ll be their favourite tradie in no time.
    
    

• Compliance with regulations

  • No one likes fines or paperwork (okay, maybe some do), but compliance is non-negotiable. Flue gas analysis helps you meet safety and environmental standards, and it’ll help to provide that all-important documentation for inspectors and insurance companies.
    
    

• Repairing flue and ventilation systems

  • Fixing a flue? Analysing it afterwards ensures the gases are venting safely and everything’s functioning as it should. No shortcuts here—this is what keeps your customers (and their homes) safe.

3. A step-by-step guide for performing a flue gas analysis

Step 1: Preparation

Before starting, make sure you have everything ready.

• Gather your tools:
  
  • Flue gas analyser
  • Appliance manufacturer’s specifications
  • Personal protective equipment (PPE) 
  • Cleaning tools for the sampling port (if needed)
• Inspect the system:
  
  • Check for visible defects or maintenance issues (e.g., cracks, leaks, or blockages).
  • Ensure the appliance is properly ventilated and operational.
• Review safety protocols:
  • Verify the work area is ventilated and free from gas leaks.
  • Wear your PPE.

Step 2: Performing the Analysis

Follow these steps to take accurate readings:

• Turn on the flue gas analyser:
  
  • Power up the analyser and let it perform its self-check and calibration.
  • Select the correct fuel type (e.g., natural gas, propane, or oil)
• Locate the sampling port:
  • Find the test port on the flue pipe.
  • There should be a small hole or a designated port specified by the appliance manufacturer.
• Insert the probe:
  
  • Insert the analyser probe into the sampling port deep enough to reach the core of the flue gases. Check for gaps to avoid leaks.
• Take readings:
  • Allow the analyser to stabilise and record key data:
    • Oxygen (O₂)
    • Carbon monoxide (CO)
    • Carbon dioxide (CO₂)
    • Flue gas temperature
    • Combustion efficiency
• For some systems, additional parameters like nitric oxide (NO) and nitrogen dioxide (NO₂) may also be measured.

Step 3: Interpreting results

• Compare to the manufacturer’s specifications:
  • Match the readings against the appliance’s optimal combustion values.
• Adjust the system (if needed):
  • If readings indicate inefficiency or incomplete combustion:
    • Adjust the air-to-fuel ratio or burner settings.

Step 4: Finishing Up

Wrap up your analysis to ensure the system is safe and ready to use.

• Record results:
  
  • Document all readings, adjustments, and final results for maintenance records or compliance purposes.
• Seal the sampling port:
  
  • Securely close the sampling port to prevent leaks.
• Turn off and clean:
  
  • Power down the analyser and clean the probe following the manufacturer’s guidelines.
• Verify:
  
  • Run the appliance again to confirm it operates correctly after adjustments.

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