This article describes the procedure to calculate air density given the temperature, dewpoint and pressure or temperature, pressure and relative humidity. Included on the page are online calculators.
How hot air balloons fly: because the hot air inside the balloon is less dense than the air outside of the balloon. The principle is really very simple; hot air rises and cold air sinks.
A hot air balloon is a relatively simple craft. To help ensure the safety of pilot and passengers, a hot air balloon may carry several pieces of safety equipment.
Commercial Propane is sometimes supplied as a mixture of propane and other Liquifed Petroleum Gases (LPG) such as butane, butylene and propylene. Autogas, in most parts of Australia, is a mixture of LPG gases including propane. LPG mixtures can be used as hot air balloon fuel provided adequate fuel pressure can be obtained.