Fondue sets come with one of three different fuel sources: alcohol burners, gel packets including sterno and newer butane burners. Alcohol burners, commonly packaged with fondue sets, provide enough heat for meat and cheese fondues, but too much for delicate chocolate sauces. Gel fuel contains a gelatinized alcohol fuel and can be used for the same applications as alcohol with less concern for spillage compared to completely liquid alcohol fuel. Butane provides an adjustable source of heat. Look for specialty burners for this fuel as an additional accessory for your fondue pot because your set most likely did not come with a more expensive butane burner. You can also use candles, which barely warm the food inside a fondue pot and need to be reserved for chocolates to prevent burning.
Alcohol will burn about 90 minutes with 3 oz. of fuel. Alcohol burners contain a gauze pad to absorb the alcohol and help prevent it from accidental spillage. Use only denatured alcohol, don't overfill, and don't add fuel while the burner is turned on or while still hot. When cooking is complete, extinguish the flame with the burner cover. Alcohol presumably burns hotter than paste fuels, and is preferred for cooking meat and broths in a fondue.
Paste gel fuel - The paste gel fuel units are flat and fit in most fondue fuel containers designed for gel fuels. Just pull off the foil top and drop into the fuel unit. (Buy) Canned Sterno - Depending on your unit the burner may accommodate a single use can of sterno. Sometimes you can just substitute the sterno can instead of the burner unit. Check to make sure you have adequate clearance. Sterno Gel (Bottles) - Some fondue units have refillable burners. Just pour in bottled sterno gel. This product is typically available in any hardware store.