A stove that split along its length is tahor, but [if it split] along its width it is tamei. A kupach that split either along its length or along its width is tahor. The courtyard of a stove: When it is three fingerbreadths high it contracts tumah via contact and via airspace, [but if it is] less than this [then] it contracts tumah via contact but does not contract tumah via airspace. How is it measured? R’ Yishmael says: One places the spit from top to bottom and [the area] opposite [the spit] contracts tumah via airspace. R’ Eliezer ben Yaakov says: [If] the stove became tamei, the courtyard becomes tamei, [but if] the courtyard became tamei, the stove does not become tamei.