Guys, the fairings panels are non-persistent debris. Don't worry about Kessler Syndrome.

As for how the broken-off bits behave after deployment, they are handled as solar panel pieces or engine fairings. They aren't fully persistent (which is good if you like your framerates to be a two-digit number). That doesn't mean they aren't solid objects, however. Point away from face.

Source

Instead of going on rails, they disappear. Don't worry about bloated part count, Kessler Syndrome or debris fields, the stock fairings won't be causing any problems like that - the fairing as a whole is just one part that is divided up into various sub-parts or panels that disappear completely.

Just thought I'd make a post about this as I've seen too many uninformed people.

EDIT: Shit, just realised the title typo.

EDIT 2: I get it - you should be jettisoning your fairings before this is a problem you need to worry about i.e. while suborbital. That doesn't change the fact that I saw a lot of people who were unclear on how the fairings actually operated.