Macworld Expo attendees (and anyone else) flying to or within the United States will be affected by a new set of rules implemented recently by the U.S. Department of Transportation that limits how and where air travelers can carry spare lithium batteries for their electronic devices. Effective 01-Jan-08, the rules prohibit carrying spare batteries in checked luggage, and limit spare batteries brought aboard in carry-on luggage.

The DOT recommends carrying electronic devices with you (we do, too, considering how often our checked luggage has gone astray), but if you wish to pack an electronic device in your checked luggage, you may pack it with its battery installed - as long as the device is securely turned off. You must protect the terminals of spare batteries in your carry-on bags to avoid short-circuits; the DOT provides how-to tips for safely covering battery terminals, such as using the plastic slip-cover that may have come with the battery, or electrical tape over the terminals.

The battery guidelines specifically refer to cell phone and laptop spare batteries, but apply to all lithium and lithium metal batteries, also common in digital cameras and camcorders, portable DVD players and video games, etc. Check the DOT Web site for specific limits on the allowed lithium content per battery, which is especially important if you have an extended-life battery.

Concerns about Sony-made laptop batteries overheating, leading to battery recalls by Apple, Dell, and several other laptop manufacturers in 2006, make this the most rational and least arbitrary restriction on passenger baggage we've seen affecting air travelers in recent years. (For details on that recall, see "Apple Recalling 1.8 Million Laptop Batteries," 2006-08-26.)