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A small butane torch

Blow torch is a common name for a simple heating torch, which burns liquid fuel with ambient atmospheric air after vaporizing it using a coiled tube passing through the flame. In the United Kingdom the older, kerosene-fuelled, type was called a blowlamp. In technical or trade usage, modern torches are never called "blowtorches"—they are instead referred to by the type of fuel they actually consume. For example, a "propane torch", "acetylene-air torch", or "oxyacetylene torch". Some torches are also named for their intended use: "cutting torch" and "plumber's torch" for example. Informed users of torches would only say "blowtorch" when speaking of old-fashioned tools that burn a liquid fuel using a vaporizer. In common parlance by uninformed speakers, however, the term is frequently used as a placeholder for any type of torch.

Modern torches will typically run on propane or butane cartridges, or be fed from a liquid petroleum gas cylinder via a hose. They produce a much larger, softer flame than an oxyacetylene torch and are used for low temperature applications — soldering, brazing, melting roof tar, or pre-heating large castings before welding, such as for repairing cast-iron cylinder heads, and for direct rapid application of heat in cooking. They cannot be used for welding, but find many other uses, not least because in their simplest form of a disposable canister feeding a hand-held torch they are very cheap and highly portable, and because the LPG fuel is very cheap in comparison to acetylene and oxygen. These torches are most frequently called "blowtorches" by non-torch-users, but are called "propane torches" by those who use them for work.

An old-fashioned kerosene blowtorch

Older blowtorches used liquid fuel such as kerosene in the form of paraffin oil, or gasoline and more recently biodiesel. These are largely obsolete, and may be difficult to start, requiring pre-heating with methylated spirit. If any doubts exist as to the integrity of the pressurized fuel tank or any of the seals in the torch, it should be treated strictly as an antique — if the tank bursts there is a very real risk of explosion or fire. These devices are properly called blowtorches.

Website with information about gasoline blowtorches

• Propane torch
• Oxy-fuel welding and cutting
• Gas burner