What is the name of the burner system that heats air inside a modern hot-air balloon?

A propane burner is the burner system that heats air inside a modern hot-air balloon.

The burner mixes liquid propane with air and ignites the mixture, producing a powerful flame directed into the envelope. Heating the air lowers its density relative to the cooler surrounding atmosphere, creating buoyant lift.

Pilots operate the burner in short bursts to increase the temperature inside the envelope and climb or maintain altitude. To descend, they normally stop heating and may open the envelope’s parachute valve to release hot air.

The burner heats the air rather than filling the envelope with propane. Propane is stored in tanks in the basket, while the envelope contains ordinary air. This distinction separates a hot-air balloon from a gas balloon, whose lift comes from helium or hydrogen.