TSA is currently deploying hundreds of full-body imaging machines at U.S. airport checkpoints.  Here's what you need to know:

- Can passengers avoid the body screening?  At most airports, TSA has scanners in some lanes and traditional walk-though metal detectors in others.  You can try to pick a lane with a metal detector if you pay attention. If you end up in a body-scan line, you can refuse to undergo the scan, but that will result in a full-body pat-down.

- Can a female passenger request that a female perform the body scan (and vice versa for men)?  No, travelers don't get to specify whether a man or woman views your scan image.

- How can passengers safequard their possessions while undergoing the body screening?  Watches, wallets and jewelry should go into carry-on bags so they aren't sitting out in the open during the scan.  While being scanned, passengers will be separated from the X-ray belt, although it will be within view most of the time.

- What else should I know to make the screening go smoothly?  Don't wear loose pants that will fall down without a belt.  Minimize jewelry, at least until inside the secure area.

- How dangerous are the new body scanners?  The TSA says the machines have been approved by the Federal Drug Administration and other agencies as safe for human use, even for pregnant women.  TSA also says the dose the X-ray machines are using amounts to less than 10 microREM of radiation, which is the equivalent to the exposure each person receives in about two minutes of airplane flight at altitude.  A different type of body scanner at airports called a millimeter wave technology, bounces electromagnetic waves off the body to create a black and white three-dimensional image.  The energy projected by the millimeter wave technology is 10,000 times less than a cell phone transmission.  

- If I have a complaint?  Write to TSA-ContactCenter@dhs.gov