What is this?

[Lemonandlime123]

Just pulled out the bed in our room and found this on the chimney breast. We had a gas fire fitted in the lounge, which is directly below our room, two years ago. Flue was lined by the company who installed it - has the lining failed?

Looks like damp to me, sorry. The type where the salt leaches out to the surface and causes that bumpiness. The discolouration above looks damp too. Does it feel damp? If it's your chimney breast it would be worth checking the flashing etc. Know anyone with a drone? Good luck.