Why is my furnace blowing cold air after blowing hot air?

Obviously you are using gas for heat. There is a temperature delay relay that makes the fan turn on when it is hot in the heat exchange area of the unit. That insures only hot air blows into the home. It also doesn't turn off the fan until the temp requirement is met on the low side. Ie cool air once the flames go out. There may be an adjustment, but most newer units need a pro to come do that. The basic idea is to give the home owner all the heat they paid for.

Your furnace turns on and heats the air in the heat chamber. When the chamber gets hot enough the fan comes on. When the thermostat in the house is satisfied the heat source is turned off and the fan stays on long enough to cool down the heat chamber. Hope this helps.

This is basically normal. The fan keeps blowing after the burner turns off to cool off the heat exchanger. It shouldn't be on long enough to make you uncomfortable though.

Yes, it is normal for the fan to run for a while after the burners shut down to cool off the heat exchanger.

Yes because the flames heat the air. When the flames turn off it's not getting heated anymore

your blower is on a delay switch,so it keeps running after the burners call out,this gives the blower time to blow any fumes,heat,out of the vents before it shuts down,this can prevent allot of problems not to mention an explosion of built up fumes and gases,its a safety feature. and a good one,hope this helps

Its the cool down cycle which is total normal.

It must be a politician...