"Oupasanam" is a nithya karma which does not require updesam from anybody.
This will be started from vivaham and it should be done till the end of life of the male person without break.
A gruhastan can simply do this twice every day, but keeping the agni without going off, and this agni should be carried by the person
to all places wherever he go (if he could return home within next 12 hours or before next period of this karma) are very very difficult to practice,
hence it is not followed by anybody.
It is entirely different from Agnihotram which is described in this thread.
For your reference, here the audio of Sri Sri Anna about 'Oupasanam' in the below video:

Note:- Sorry for the very delayed reply!

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