Smoke, whether from cooking, cigarettes or fire, can ruin some electronic devices. Many devices have cooling vents and holes for switches and connectors through which smoke can seep, coating sensitive parts with resin and particles. Some electronics, such as digital watches, are sealed against the outside and don't malfunction from the effects of smoke. But other electronics, such as computers, televisions, and stereos, can be destroyed from long-term exposure particularly to cigarette smoke.
Most electronic components, such as transistors, capacitors and resistors, have metal or plastic cases that protect them from environmental hazards such as smoke. Over a long period, however, a build-up of smoke material acts as a blanket, reducing a device's ability to lose heat and making it run hotter than normal. Excessive temperatures shorten the lives of most components, especially transistors, integrated circuits and other expensive items. The tar in cigarette smoke causes dust to stick to components, worsening the heat problem.
A circuit board is a flat piece of epoxy and fiberglass bonded to thin sheets of conductive copper. The copper connects electronic components mounted on it into a functioning circuit. The board is a good electrical insulator, but when smoke settles on it, tiny electrical currents flow where they normally should not, particularly in high-frequency circuits in radios, televisions and computers. These unwanted currents cause the equipment to behave erratically -- your computer may reboot itself for no apparent reason, for example.
Though modern television sets and computer monitors have a flat-panel design based on liquid-crystal display, or LCD, technology, older equipment contains cathode-ray tubes, or CRTs. CRTs operate on electricity in excess of 15,000 volts. The high voltage produces static electric fields which attract dust and smoke particles from the surrounding air. An accumulation of smoke on high-voltage devices causes arcing, or electrical sparks, and premature equipment failure.
Before the 1990s, computer hard drives were dishwasher-sized devices with their own air filters. Dust and smoke particles caused catastrophic damage to their internal mechanisms. Though current hard drives have sealed mechanisms, their circuit boards are partly exposed, so you should still keep them away from prolonged exposure to smoke.
DVD and CD drives use precision optics to guide a thin laser beam to the surface of a disc and detect the data on it. Smoke particles can foul the optics, causing audio and video to stutter; in extreme cases, the drive may not be able to read the device at all. Carefully cleaning the optical drive's lens usually cures the problem; the damage is seldom permanent.