Can I use ordinary expanding foam around a pipe?

No. The foam you buy at a builders' merchant burns.

It fills the gap, sets hard and looks tidy enough to pass a quick glance. But in a fire it does nothing for you, and it can feed the flames.

Fire foam is a different product. It's usually red or pink, like the foam in the photo, and the can has a fire rating in minutes on the label along with the test standard it was approved to.

Even then, that rating only holds for the gap it was tested on. A 15mm hole round a copper pipe in a block wall isn't the same job as a 60mm hole in plasterboard round a bundle of cables, and you could fill both with the same red foam. One might pass and the other not.

So read the data sheet before you trust a can. And if you can't tell what the last trade used, photograph the gap and send it over. We'll tell you what we think it is.