It's almost certainly fine. It's probably in the flame area, not the air path. If it's in the flame area, and the heat exchanger is sealed, there are no problems. If the heat exchanger is leaking, carbon monoxide is a far, far greater threat to your health than is asbestos.
Asbestos fibers, roaming through the air and into your lungs, are a reasonably bad thing.
Asbestos, in place, undisturbed, contained, not at all crumbling into the air, is a properly good insulator.
You're overreacting.