A combustion analysis measures how completely and safely a gas appliance is burning fuel, not just whether it turns on.
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Quick answer
Combustion analysis is a diagnostic test where a licensed technician inserts a calibrated analyzer probe into the flue of a gas boiler or water heater to measure flue gas readings such as oxygen, carbon monoxide, and flue temperature, which together indicate whether the appliance is burning fuel completely, safely, and efficiently. It goes beyond simply confirming the unit fires, since a unit can appear to run normally while still combusting poorly due to an air or fuel imbalance. It is a standard part of thorough maintenance and troubleshooting on gas appliances, particularly after any repair affecting the burner, gas valve, or venting.
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A gas appliance can look completely normal from the outside, firing on command with what appears to be a reasonable flame, while still combusting inefficiently or unsafely underneath that surface impression. Combustion analysis exists because the human eye cannot reliably judge the fine balance between air and fuel that determines whether an appliance is running clean or producing elevated carbon monoxide and wasting fuel. A calibrated analyzer gives an objective, repeatable reading rather than a visual estimate.
This matters even more on tightly sealed, well-insulated homes, increasingly common in Metro Vancouver renovations, where reduced natural air infiltration can affect how appliances draw combustion air compared to older, leakier construction.
Working carbon monoxide alarms on every level of the home, particularly near sleeping areas, are the homeowner's own first line of defence and should be tested regularly with fresh batteries. Any headache, dizziness, or flu-like symptom that improves after leaving the house and returns when back inside should be treated seriously and reported immediately, along with having the home's gas appliances checked. Combustion analysis itself requires calibrated equipment and training to interpret correctly, so this is not a test a homeowner can perform or meaningfully approximate at home.
If a carbon monoxide alarm sounds, leave the home immediately, and treat that the same as a suspected gas leak until a technician confirms the appliance and venting are operating safely.
| Finding | Typical outcome |
|---|---|
| Readings within normal range for the appliance | No action needed, documented as baseline for future visits |
| Elevated carbon monoxide reading | Appliance taken out of service until diagnosed and corrected |
| Poor draft or spillage detected | Venting inspected and corrected before returning unit to service |
| Readings suggest an air or fuel imbalance | Burner and gas valve adjustment, followed by re-testing |
Safety note
Any work on the gas train, venting, or combustion side of a boiler or water heater must be done by a Technical Safety BC licensed gas fitter; CANRO holds gas licence LGA0043870 and boiler licence LBP0046450. If you ever smell gas, leave the home immediately and call FortisBC at 1-800-663-9911 before doing anything else.
It is a diagnostic test using a calibrated analyzer to measure flue gas readings such as oxygen and carbon monoxide, confirming a gas appliance is burning fuel completely and safely rather than just turning on.
It is commonly included in a thorough annual maintenance visit and is also performed after any repair affecting the burner, gas valve, or venting.
No. This test requires a calibrated analyzer and training to interpret correctly, and is performed by a licensed technician as part of maintenance or troubleshooting.
Not necessarily. An appliance can appear to run normally while still combusting inefficiently or unsafely, which is exactly why an objective analyzer reading is used rather than a visual check alone.
Leave the home immediately and treat it with the same urgency as a suspected gas leak until a technician confirms the source and that appliances are safe to use again.
It can. Reduced natural air infiltration in a well-sealed home changes how appliances draw combustion air compared to older, leakier construction, which is one reason combustion analysis is worth doing after major renovations.
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