The domestic blowtorch, shown here, utilizes disposable bottled-gas cartridges.
For use, the gas cartridge is first fitted into the cartridge holder. The
valve unit is then screwed into the cartridge holder, the pin it contains
piercing the gas cartridge. When the needle valve is opened by turning the
control knob, gas is allowed to pass through the filter to the burner head.
As the gas flows through the burner head, air is drawn through the holes
provided, allowing a hot flame to be ignited outside the mouth of the burner
Often a variety of burner-head attachments are supplied, producing different
flame configurations suitable for specific jobs.