I would like to know if you can apply a fire retardant weatherstrip on a fire door. The door currently slams shut and are quite noisy so I’m hoping to apply this as a cushion to reduce the noise but will this be breaking any regulations for a Fire Door?

Batwing type seals are available for use with fire resisting doors.  This type of seal fits inside the door frame rebate so you have to ensure they can be fitted without affecting the self-closing action of the door.  There are single wing versions too.

Thank you for your reply on this. Just to supplement what I mentioned here the weatherstrip I'm using is Fowong Adhesive Weather Stripping Foam Tape 6mm(W) x 3mm(T) Window Door Draught Excluder SoundProof Weather Strip Tape Seals for Gap Seal (fire retardant material) which I am thinking of applying as shown in the attached photo along the right hand side of the frame and along the top (it's the black tape next to the grey intumescent fire & smoke seal ). The gap between the door and the frame with this does become less than 3mm when attached. In terms of the angle it's applied in a similar position to the batwing type seals you sent here.

With the foam tape fitted, will the door self-close completely to the rebate stop of the door frame and so that the latch bolt engages fully?  What happens when you try to burn the foam tape?