I am not an expert, but I would think it would be safe to use the
kiln if the cord and plug are in perfect to condition.
I would strongly advice that to be on the safe side, I would have it
checked out, and if necessary have the cord and plug replaced.
If there is a ceramic supply house or a kiln dealer in your area,
they usually have someone who does repairs on kilns and can advise
If it is a small table top kiln, a cloth covered cord may be o.k.,
but anything larger should have one of the new cords and a polarized
In other words, the kiln itself would not be a problem, but the cord
may well be.