If you're flying, you may get pulled aside by a TSA agent for a swab test. Also, your baggage may get swabbed. The purpose of the test is to check for chemicals that might be used as explosives. The test can't check for all the chemicals that might be used by terrorists, so it looks for two sets of compounds that can be used to make many types of bombs: nitrates and glycerin. The good news is the test is highly sensitive. The bad news is, nitrates and glycerin are found in some harmless everyday products, so you could test positive.
Getting swabbed doesn't seem to be particularly random. For example, some people get swabbed nearly every time they fly. This may be because they've tested positive before (possibly related to a penchant for making smoke bombs and other small pyrotechnics) or because they meet some other criteria. Just expect to be swabbed and be prepared.
Here's a list of common chemicals that may cause you to test positive. Avoid them or else be ready to explain the test result, because it can take a while for TSA to complete its evaluation of your belongings, which can translate into a missed flight.
Common Products That Test Positive
- Hand soaps that contain glycerin (Rinse very thoroughly after washing your hands.)
- Lotions that contain glycerin
- Cosmetics or hair products, which may contain glycerin
- Baby wipes, which may contain glycerin
- Certain medications (such as nitroglycerin and other nitrates)
- Lawn fertilizers (Nitrates: Wash your hands and especially your shoes.)
- Fireworks and other pyrotechnics
What to Do If You're Flagged
Avoid becoming hostile and aggressive. It won't speed the process. You're likely going to get patted down by an agent of the same gender who will also empty your bag for additional testing. There's a chance your luggage may get pulled, although this rarely happens; it's also unlikely that you will miss a flight because of the test.
Be aware of chemicals in your environment and able to trace your steps to help TSA identify the source of the triggering compound. Sometimes you won't have any idea why you flagged the test. But, careful attention to hygiene may help you avoid the situation. The best advice is to arrive early enough before your flight to get through security. Try to avoid the problem, plan for it, and don't overreact if it happens to you.