I’ve lived in my 1st floor flat for almost 4 years and have never had any issues before like this. We’ve had the windows open all summer every year and apart from the odd fly it was never a problem. Around 3 months ago we started noticing what we thought were fruit flies. I tried the trap with apple cider vinegar and dish soap but they weren’t attracted to it. I’ve not noticed any of them near our fruit either. It’s winter here in London but we do still open the windows to air the flat out a bit. I’ve tried to clean the drains over those months with bleach and also white vinegar and soda crystals. I’ve checked the bathroom drains and have done the same. I’ve poured kettles of boiling water down all sinks and shower drains too. Nothing has helped. We’ve pulled out all furniture and hoovered behind it. I even pulled out the panelling at the bottom of the kitchen cupboards and pulled out all food in the cupboards. There’s nothing coming from in there or underneath. They are not accumulating anywhere and I can’t find where exactly they are coming from. It’s a 1 bedroom flat and they are in every room/area. Not a lot but maybe 1-2 per room. They are very quick and I try to swat them but they always get away. What could they be attracted to? I’ve checked the hallway outside and they aren’t out there. I’ve got some damp and cracked grouting on my shower tiles in the bathroom which is being re-grouted today (which will help the damp stop as water was getting behind the tiles via the crack). My landlord has left it like this for around 1 year and I worry that they might be coming from there… I have no idea though 🤦🏻♀️ Has anyone else had this problem?