The barashnum was once a requirement rather than a specialism. Texts preserved from the Sasanian period and later treat it as the remedy for grave pollution and expect lay people to undergo it, and the ritual apparatus assumed by the Vendidad is that of a community in which such purifications are ordinary. That is not the modern picture. Among the Parsis of India the rite survives principally as a stage in the making of a priest, undergone before ordination, and it is administered at a small number of institutions equipped for it.
In Iran it has largely lapsed. The reasons are ordinary ones: the rite is long, it requires specialists and a prepared space, one of its materials is difficult to obtain and use in an urban setting, and the underlying purity rules have themselves been argued over within the communities. Zoroastrian reformers from the nineteenth century onward questioned whether such observances belonged to the religion's core or were an accretion, and traditionalists answered that the purity laws are integral to it. That argument is live. The atlas therefore records the historical practice as attested and its present extent as contracted, without treating either the reformist or the traditionalist reading as settled.