Combustion Testing

Combustion Testing ensures safe and efficient burner operation

For natural draft equipment insert the probe for the combustion analyzer into the venting before the draft hood.  For induced draft equipment insert the probe for the combustion analyzer into the venting a minimum of 12″ above the outlet of the inducer fan motor and before any dilution air. All readings should peak and stabilize within 5 minutes of startup and CO readings must be less than 100 PPM.

Minnesota State Mechanical, Fuel and Plumbing Code states:

  • Air-Free Carbon Monoxide readings in the Flue above 400 PPM (.04%) is unsafe to operate.
  • After 5 minutes in steady state operation.
  • Before the draft hood if applicable.

Notes

  •  “Air-Free” Carbon Monoxide readings are different than “Mixed Air” readings. “Air Free” Carbon Monoxide readings are higher than “Mixed Air” readings because “Mixed Air” readings are diluted with excess air.
  • Most technicians reference “mixed air” readings which are lower than “Air-Free” readings.
  • The purpose of “Excess Air” is to ensure adequate combustion air by providing more than is needed.
  • It is easy to confuse the two readings and the technician needs to be certain which he or she is referencing when inspecting a heating appliance.

High Carbon Monoxide in the Flue

Often times a plugged heat exchanger or venting will cause excessively high CO in the flue.