The sixth of the eight major hells is the Hell of Burning Heat, which is located beneath the Hell of Great Wailing and is the same size. Various types of sufferings exist in this hell. Placed in the Jambudvīpa (the world), a tiny flame of fire in this hell, as small as a bean, will burn anything completely in no time, not to speak of the bodies of sinners, which are as soft as cotton. The intensity of heat from this hell fire is such that in the eyes of sinners in this Hell of Burning Heat, the fires in the five hells mentioned above will seem like snow. For instance in the human world, flames of hot iron and copper are hotter than those of firewood.

Suppose 1,600 years in the human world correspond to one day and night in the Paranirmitavaśavartin Heaven, the sixth heaven in the realm of desire, where the life span of heavenly beings is 1,600 years. Suppose 1,600 years in the Paranirmitavaśavartin Heaven are equal to one day and night in the Hell of Burning Heat, the sinners in this hell live as long as 1,600 years.

Ken Hōbō-shō, A Clarificaton of Slandering the True Dharma, Writings of Nichiren Shōnin, Doctrine 3, Pages 109-110.