The lower, open part of a hot-air balloon envelope is called the skirt.
The skirt hangs below the main envelope and surrounds the opening through which the burner heats the air. It helps guide the hot air into the envelope and provides some separation between the flame and the fabric above. The skirt is commonly made from heat-resistant material and is designed to tolerate the intense thermal environment near the burner.
A balloon’s burner frame and basket are suspended below the envelope by load lines or cables. The skirt is part of the envelope assembly, not the passenger basket and not the burner itself. Its size and construction vary among balloon designs.
Balloonists must inspect the skirt carefully because damage near the burner can affect safety. The crown at the top of the envelope has a different function: it contains the deflation system used to release hot air during descent and landing.