Any chance you’ve got incense or a oil burning going off nearby?
Maybe a humidifier. If you’re pushing moisture in the air or use it near the bathroom after a hot shower, might something could be being pulled in and reacting with the filters. Anything on the display screen?
Nothing showing on the air quality screen, the line is green and at the bottom of the graph. We haven’t had any candles or humidifiers on in the bedroom or living room, and we haven't used this in the kitchen, so it's not been processing air with cooking smells or anything.
It's not normal for the filter to trap oils though is it? I don't think the filter could be working if it had and is then putting out air with a smell?
It sounds like it’s reacting to something in the air. If there was a larger issue afoot I would have thought it would of been experienced from day 1. Might be best to give the unit a clean over, ensuring there isn’t anything or residue on the surface. This post might help you there - Keeping your purifier performing at its best | Dyson Community.
The other suggestion is to power it onto 10 for the next hour or two and see if that solves it. If not, try the website diagnostics for next steps 
! https://www.dyson.co.uk/support/journey/troubleshooting/386320-01.
The filters have been removed for their packaging right? If they have, may I suggest removing them from the unit and running it without them in. If the smell is gone, you know the issue is with the filters reacting to something in the air.
Hello @57James
If you removed the plastic from the filters and still notice the same odor. I recommend you to stop using your machine and request that you contact our local customer support team via their WhatsApp channel. They will be able to run through precise diagnostics to pin point the cause of these issues and discuss the next step. You will need your machine to hand when making contact.
To contact the team, simply click on our Guides and manuals link, navigate to the ‘Contact us’ section of the page and start a WhatsApp conversation.
If you'd prefer, you're welcome to call the Dyson Helpline to speak with our experts directly. You can find their number in the ‘Contact us’ section of the page.
Thanks for helping folks, and apologies I went to thumbs up Kibbleb's comment and accidentally selected it as the answer, I don't think I can deselect!
But it did help narrow things down, I removed both filters on each side, making sure there weren't any stray plastic wrappers, then ran the machine without them. So without them the air appears not to have any odour!
Is this a common issue with these filters? Even if it pulled in air with a smell, I'm thinking perhaps the kitchen door was left open and the smell wandered upstairs - shouldn't this system pull that through the filters and put out fresh air? Or are smell particles smaller than PM2.5!? I don't know anymore 
It should. I’d lean towards it not cured correctly in manufacturing or damp that got into the filters when being shipped. A replacement set should see you right! If there’s no stock, push for an exchange!
