The working time of a can of gas in box furnace depends on many factors, such as the full use of large firepower, the intermittent slow fire of small firepower, the capacity of gas tank and so on. Generally speaking, a 220-gram or 230-gram fuel tank can provide about 2 to 3 hours of battery life, while a 250-gram fuel tank can provide about 3 to 4 hours of battery life. However, if the small fire is intermittent, the service time of these gas tanks can be extended to 5 to 7 hours.