Can you tell me if there is any benefit of having flush double fire doors over rebated double fire doors.

Also in what event would I need to fit a door selector? Would there ever be a need for one with a flush double fire door set?

It depends on the purpose of the fire doors, if they are smoke stop doors dividing up a corridor then flush jamb doors are acceptable and even fire doors, depending the test data for the fire doors. If they are fire doors then rebated doors are more effective but you then need door selectors to ensure the doors close in the correct order. Why would you need to fix door selector to a flush jamb double fire door set it doesn't matter which doors closes first?

I had spoken with someone regarding what is more suitable for a set of fire doors between flush and rebated and they advised that rebated fire doors were more suitable and I wandered why this would be.

He also said that he has had some cases where the door selector was fitted to flush doors and as you are I was unsure of why this would ever be done.

I suspect the heat builds up as it tries to pass around the rebate consequently activates the intumescent strip quicker but that is only a guess and you would need to do some research with one of the testing companies.

If the centre jamb of a pair of fire doors is rebated then you need door selectors to ensure the doors close in the correct order this does not apply to flush jamb double fire door as it doesn't matter which doors closes first, simples?

On double doors, whether they are FD30s or FD60s, do you require one door stile/edge to have the intumescent fire/smoke seal or do both door meeting stiles require the intumescent fire/smoke seal on the door leading edge?

Thanks Kulvinder

The meeting stiles require two intumescent strips next to each other on one leaf similar to what you would do on a FD60 fire door. Check it out on ASDMA Best Practice Guide 13.3.