How do I disconnect a butane cylinder?

Turn the control lever from the vertical (on position) to the horizontal (off position). With your hand over the regulator, which is usually a round metal device, normally blue in colour or it has a blue label or label that says butane connected to the bottle by a hose what controls the gas flow. Place your thumb against central spindle/shaft of control lever and press firmly towards the body of the regulator. This will release the locking collar from the cylinder valve and regulator should spring away. The cylinder can then be removed for the replacement cylinder to be positioned.