ER has many old coaches so it is not a tough task for ER to find old coaches for isolation coach. But some zones r finding it tough to find and use old coaches for isolation coach. Some zones like SER has many 15 to 20 or till 25 yrs old coaches which are currently used in many trains, specially HTE CDO, TATA CDO has many such coaches which is used in many of its Express/ superfast/ passenger trains. So for them it is a problem to use them.