Had a cleaning job on a PC which is about 3 years old, cigarette smoke and dust had not yet caused any hardware damage or severe overheating but only a matter of time would have seen problems. I'm a 20 a day smoker and even the sight and smell of this machine was enough to make me want to barf! 
Pics taken on phone camera but you get the idea...

Pics taken on phone camera but you get the idea...










