HEET is a fuel that backpackers and campers sometimes use as fuel in their alcohol stoves. It is readily available in most countries and its official purpose is to dry fuel lines and prevent them from freezing.
In the United States, HEET comes in two variations: yellow bottles contain Methanol (methyl alcohol, CH_3 OH) and red bottles contain Isopropanol, (isopropyl alcohol, C_3 H_7 OH, or IPA), otherwise known as IPA. Isopropanol (red bottle) is a smoky, dirty and sooty fuel that has an unpleasant smell. Some users report of feeling unwell after inhaling fumes when using it as a fuel. Although methanol is toxic to humans, of the two types of HEET, the preferred HEET is Methanol (yellow bottle), which burns cleaner than Isopropanol (red bottle).