lethal service consideration in pressure vessel design 2

Dear All,

ASME defines well what to do in "lethal service". In my companies case we are building pressure vessel for chemical process where this chemical will not be in contact with vessel skin/material or any nozzles and mountings. process will conduct in small confined area in the vessel where it is covered by big layer of insulation/ refractory(@20 inches). My question is in this situation does ASME rules for Lethal services is applicable? or Is there any special regulations for this type of case?

Thanks in Advance,