Their fans running at max (or a very warm device) would let them know. This has been the experience among the non/less-technical users in my company.
I think it would be smart to educate people as part of a regular security briefing for non technical staff though. But if it's something that high of concern to your company maybe an automated CPU usage monitor could alert the team to anomalies.
[1] I was running a test today when the program being tested ran into a very tight loop and the fan really kicked in. I was curious if it would finish and let it run for several minutes until all went quiet and the screen went dark. It had shutdown to prevent heat damage.
A laptop overheating from few minutes of 100% CPU is not normal.