Natural gas smell when heat kicks on
It comes and goes. I only smell it when the heat first comes on, it lasts for a few moments and then disappears. I don't smell anything near the furnace, but instead in the upstairs living room. I've checked that all the vents are open, and the burners are all working inside the furnace. Air filter is clean and replaced.
What am I missing? Should I just bite the bullet and call an HVAC tech?