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Recently an LLNL employee left a laptop computer on overnight in a soft carrying case, plugged into a wall outlet. The computer, an Apple Titanium PowerBook G4, was in the "sleep" (i.e., low-power) mode, with the carrying case closed. The next morning, the employee discovered that the computer had overheated to the point that the keys melted.

The damaged laptop.

This event is still under investigation by Apple engineers and appears to be an isolated case. However, many portable computers are used by LLNL employees at work and home, and this incident serves as a reminder that portable computers need to be operated with care.

What Was Learned

The cause of this incidence may have been failure of the temperature sensor to automatically power down the computer when it overheated.

Laptop computers should never be left operating overnight in a soft carrying case or on any other soft surface (even in the sleep mode).

The bottom of the Apple computer case functions as a cooling surface to transfer heat from inside the computer to the cooler outside air. The case bottom is slightly raised to allow the airflow needed to cool the computer while in use.

The instruction manual for the Apple computer clearly warns never to operate the computer on a soft surface, which can block the airflow vents underneath the computer, causing it to overheat.

 A padded carrying case is sufficiently insulated to cause a computer to overheat, even in a low-power mode.

Note: This Lesson Learned is not limited to Apple computers.

User’s guides for other manufacturers' portable computers caution not to block, push objects into, or allow dust to accumulate in the air vents, as this may cause a fire.

Other manufacturers also warn against operating portable computers with the base resting on exposed skin for extended periods of time, because the base surface can become hot enough during normal operations to cause discomfort, or even burns, to exposed skin.

Recommended Actions

  • Laptop computers should always be operated on hard surfaces with unobstructed ventilation to avoid overheating.

  • If the computer must be operated on a soft surface, an optional heat sink base can be used to assure proper cooling.

  • Do not use the heat sink in a closed carrying case or similar environment that might obstruct ventilation.

  • Review your laptop computer's instructions.

Melt down
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I'll certainly review the way I use mine!





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