Chocolate does not like heat. In a vending machine, temperature matters so bars keep their shape.
Bars, chocolate, and wafers are popular in machines in offices, workplaces, universities, and stations. Chocolate is heat-sensitive, so in warmer places refrigerated machines or cooler zones work better. The producer gives storage conditions on the pack.
Temperature
In warm surroundings, chocolate softens and a white bloom may form. That usually does not mean spoilage, but it spoils the look.
Packaging
Bars usually come in flat, long packs that fit standard spirals. Chocolate tablets may need a different layout.
Where they fit
In adult settings such as offices and plants. In schools, the range is restricted by rules on food for children and young people. The page on snack vending machines (publisher's site) has examples.
FAQ
Do bars melt in vending machines? They can soften in heat. Cooling or keeping the machine out of the sun helps.
What is the white bloom on chocolate? Usually fat or sugar that surfaced after temperature changes.