Is this a charcoal tandoor or a gas one?
I have these "coals", that I never take out, in my gas tandoor
They heat up with the flames, along with the clay walls
I never have to clean them
Any dirt just burns off
My gas tandoor takes an hour and a half to heat up properly
Maybe I misunderstood and you mean clean the actual insides of the tandoor
If you do, then I use a damp cloth to clean any soot of the walls
When you properly fire it up, a lot of dirt will burn away
It will be sterilised even if it looks a bit mucky
I would leave that heating for a couple of hours, it is a bit black, isn't it?