Home inspections are good for getting a basic look at all of the major systems and components of a home. This means that the nature of an inspection is general.
One of the general tests that good home inspectors do is to fire up the furnace. Before I was an inspector I thought, “Why should I pay for someone to turn on my furnace? I can turn on a furnace and tell if it works!” This is a fact, however, there are things that a good inspector will look for when the furnace fires up that I would not have known to look for before I was an inspector.
One of the main things that good home inspectors look at while the gas furnace fires up is the flames.
Proper operation of the furnace will have the flames turn on with a steady blue.
Once the heat exchanger is heated sufficiently the main fan (that will blow heat through the home) turns on
The flames should remain steady and blue with little to no change in shape and color when the main fan turns on
This video was taken on a recent Salem, Oregon home inspection that shows what a flame SHOULD NOT look like when the main fan initiates: