Can a desktop/laptop cause fire?

[Alex-Nigma]

Conditions:
1. All hardware is more or less new (the oldest one is an asus x75v laptop)
2. All vents are open, everything stands on solid surface.
3. Laptops and desktop are sometimes left working at night/when nobody is at home.

Question:
Is it safe to leave them working unattended in terms of them starting fire or causing other damage?

 

[BadAsAl]

Any electronic device has the potential to fail and cause an electrical fire, sure. But at my work we have a server room with 100 servers running 24/7 and they have never had a problem with fire. There is a fire suppressant system in place of course in the even it does but it has never needed to be used.
So I think it is as safe to leave computers running as long as you take reasonable precautions, i.e. not run them in a hot or moist environment.

 

[Phillip Corcoran]

They'll be fine, a PC or laptop should automatically shut down if internal temperature gets too high (unless the PC has been built with cheap parts by someone who doesn't know any better, and the internal/external wiring is dodgy).

However, I'd advise you to put them in sleep mode when nobody will be at home (if you don't want to shut them down).