Related Clues:

• Burn it by stepping on it
• Windbag's output
• Balloon contents
• Petrol
• Filling-station supply
• Bombas-tic talk
• 21-Across, for one
• Atmosphere makeup
• Station ration
• Nitrogen, for instance
• Balloon fill
• Swell time
• Stove fuel
• Rip-roaring time
• Blowtorch fuel