Combustion analysis and FGA readings: what the numbers mean
A flue gas analyser samples the exhaust gases leaving a boiler and reports carbon monoxide, carbon dioxide and calculated efficiency. The figures either confirm the burner is set correctly or point to a problem.
Where flue gas analysis usually comes from
High carbon monoxide relative to carbon dioxide usually means incomplete combustion, often from restricted air supply, a dirty burner or a fault in the gas valve or oil nozzle setting. Low measured efficiency can point to scale on a heat exchanger or an incorrectly set air-to-fuel ratio. The reading is taken with the appliance at working temperature and recorded on the service paperwork left with the customer.
Published business details
- Based at 24 Bristol Road, Radstock, BA3 3EE
- Telephone enquiries: 07516 118198
- Opening hours: Monday to Friday, 8:30am to 5:00pm
Flue gas analysis — the facts that change the job
- CO to CO2 ratio is the key indicator of clean combustion
- Readings are taken at working temperature, not on start-up
- A high reading can mean restricted air supply or a dirty burner
- Analysers are calibrated regularly to stay accurate
- Results are recorded on the service report for future reference
Questions we get asked
- What is a bad CO reading?
- There is no single universal cut-off since it depends on appliance type, but a reading outside the manufacturer's tolerance means the appliance needs attention before being left in use.
- Does every service include combustion analysis?
- It should for any appliance where testing is practical, since it is one of the few objective measures of how safely and efficiently a boiler is burning fuel.
Related help pages
- Gas safetyGas tightness testing: how a suspected leak is actually checked
- Gas pipework safetyCapping a redundant gas supply: why it cannot be left open
- Efficiency checksCondensing efficiency checks: is your boiler actually condensing
- Oil compliance paperworkOFTEC service paperwork: what a CD/11 style record shows
- Scope clarificationWhy commercial catering equipment sits outside a domestic-focused service
- Brand comparisonGrant vs Firebird oil boilers
Services that cover this
Where we deal with this
Sorted quickly: flue gas analysis
In practice: Combustion analysis turns 'the boiler sounds fine' into an objective number, which is exactly why it is a core part of every service visit.
For gas work, use a Gas Safe registered engineer; for oil work, use an OFTEC-registered technician.
New Worcester boiler with a 10 year guarantee*
Free no-obligation quotes for installation, servicing & repairs across BA & BS postcodes.