What TSA scanners actually see

TSA uses two main types of scanners at airport checkpoints: millimeter wave scanners and backscatter X-ray machines. Millimeter wave scanners are far more common now. They work by sending radio waves at your body and reading the reflections—similar to how radar works, but at much higher frequencies. The scanner creates a detailed outline of your body and anything you're carrying, then software flags items that don't match expected shapes for clothing, keys, or phones.

Backscatter X-ray machines, which were phased out at most U.S. airports by 2013, worked differently. They sent a low-dose X-ray beam across your body and detected the scattered radiation bouncing back. Both types can see through clothing but cannot see inside your body or read text on documents.

The image the scanner produces is not a photograph—it's a generic outline of a person with highlighted areas where the scanner detected something dense or unusual. A TSA officer in a separate room views this image on a monitor. The officer cannot see your face, cannot identify you personally, and cannot save or print the image.

Key Takeaways

  • Millimeter wave scanners use radio waves to detect objects on your body and clothing, creating an outline image that a TSA officer reviews in a separate room.
  • The scanner cannot see inside your body, read documents, or identify you by face—it shows only a generic silhouette with highlighted areas.
  • Common items that trigger a second look include metal belt buckles, underwire bras, thick seams, and items left in pockets.
  • If the scanner flags something, a TSA officer will either ask you to remove the item or conduct a pat-down search to verify what it is.
  • Images are not saved, printed, or used for any purpose beyond that single screening—they are deleted after you pass through.

How the scanner identifies threats

The scanner's software compares the image it creates to a library of known threat profiles. It looks for the density and shape of objects—metal, ceramics, powders, and liquids show up differently than fabric or skin. When the software detects something that doesn't match the expected profile for a wallet, phone, or keys, it flags that area on the image for the TSA officer to review.

The officer then decides whether the flagged item needs further inspection. For example, a metal underwire in a bra will show up as a dense line across the chest, but the officer knows what an underwire looks like and will clear you. A ceramic knife or a gun, by contrast, would have a shape and density profile that matches known weapons, and the officer would stop you for additional screening.

The system is designed to catch items that pose a security risk—primarily weapons and explosives. It is not designed to detect drugs or contraband that doesn't pose an when ready threat to the aircraft. TSA officers are trained to recognize the visual signatures of common threats, but the software itself does most of the initial sorting.

Why some everyday items trigger the scanner

Metal objects are the most common reason a scanner flags you for a second look. Belt buckles, jewelry, underwire bras, metal zippers, and even the metal rivets on jeans can create a dense reflection that the scanner picks up. Thick seams, layered clothing, and items bunched up in pockets also show up as denser areas and may trigger a review.

Liquids and gels appear as distinct shapes on the scanner because they reflect the radio waves differently than solids. This is why TSA limits liquids to 3.4 ounces per container in your carry-on—the scanner can detect them, but it cannot determine their exact contents from the image alone. A full water bottle, a jar of peanut butter, or a tube of toothpaste will all show up as a defined shape that the officer may ask you to remove for inspection.

Shoes, especially those with thick soles or metal shanks, often trigger a secondary check. Coins, keys, and phones left in pockets are routine flags. None of these items are prohibited—the scanner is straightforward alerting the officer that something denser than fabric is present, and the officer verifies it is not a threat.

What happens after the scanner image is created

Once the scanner produces an image, a TSA officer reviews it in real time. If nothing is flagged, you move forward. If something is flagged, the officer may ask you to remove the item (like a belt or phone), rescan, or submit to a pat-down search. A pat-down involves a TSA officer using their hands to feel your clothing and body to confirm what the scanner detected.

The entire process typically takes less than a minute per person. If you are selected for additional screening, you have the right to request a same-gender officer and to have a companion present during the pat-down. You can also request a private screening room if you prefer not to be screened in public.

After you pass through, the image is permanently deleted. TSA does not retain scanner images for later review, investigation, or any other purpose. The image exists only long enough for the officer to make a go/no-go decision at that moment.

Radiation exposure from airport scanners

Millimeter wave scanners emit non-ionizing radiation—the same type used in cell phones and WiFi. Non-ionizing radiation does not have enough energy to damage DNA or cause cancer. The dose from a single millimeter wave scan is extremely small, far below the threshold for any biological effect.

The backscatter X-ray machines that were used before 2013 did emit ionizing radiation, but at a very low dose. Studies by the TSA and independent researchers found that the annual radiation exposure from backscatter screening was equivalent to a few minutes of natural background radiation you receive from the sun and soil every day. For frequent flyers, the cumulative dose over a year was still negligible.

If you are concerned about radiation exposure, you can request a pat-down search instead of going through the scanner. TSA is required to offer this alternative at every checkpoint. The pat-down takes longer but exposes you to zero radiation.

How scanner technology has changed

The TSA introduced millimeter wave scanners around 2010 as a faster, safer alternative to backscatter machines. Early millimeter wave scanners created detailed images that some passengers found invasive, so the TSA updated the software to display only a generic outline with highlighted threat areas rather than anatomical detail. This change was made around 2013 and is the standard at U.S. airports today.

Newer scanners are faster and more accurate than earlier models. Some airports have installed automated threat recognition (ATR) software, which means the scanner's computer makes the initial go/no-go decision without a human officer reviewing the image first. If ATR clears you, you proceed without anyone ever seeing the image. If ATR flags something, an officer reviews it. This speeds up screening for the majority of passengers who carry nothing of concern.

The TSA continues to test and upgrade scanner technology. Research is ongoing into even faster and more accurate detection methods, but millimeter wave scanners with ATR software are the current standard at major U.S. airports.

What the scanner cannot detect

TSA scanners cannot see inside your body, so they cannot detect swallowed items, implants, or internal contraband. They cannot read the contents of a closed book, the text on a document, or the data on a phone or laptop. They cannot determine the chemical composition of a liquid or powder—they can only see that a liquid or powder is present and estimate its shape and density.

Scanners also cannot see through lead or certain other dense materials, which is why TSA may open a bag or container if the scanner image is unclear or shows an unusual shape. If you are carrying something in a lead-lined pouch or a thick metal case, the scanner will flag it, and TSA will open it to verify its contents.

Frequently Asked Questions

Can TSA scanners see through my clothes?

Yes, millimeter wave scanners can see through most clothing, but the image is a generic outline, not a detailed photograph. The scanner shows the TSA officer only a silhouette with highlighted areas where dense objects are detected. The officer cannot see your body in detail or identify you personally.

Do TSA scanners save or store images?

No. Images are deleted when ready after screening. TSA does not retain, print, or use scanner images for any purpose beyond that single checkpoint screening. There is no database of scanner images.

What should I do if the scanner flags me?

The TSA officer will either ask you to remove the flagged item and rescan, or conduct a pat-down search. You can request a same-gender officer and have a companion present. If you prefer to avoid the scanner entirely, you can request a pat-down search instead—TSA must offer this alternative at every checkpoint.

Is the radiation from airport scanners dangerous?

Millimeter wave scanners emit non-ionizing radiation, which cannot damage DNA. The dose is extremely small and poses no health risk. If you are concerned, you can request a pat-down search instead, which involves no radiation exposure.

Why did TSA stop using backscatter X-ray machines?

Backscatter machines were phased out around 2013 because millimeter wave technology was faster, more accurate, and created less detailed images. Backscatter machines also emitted ionizing radiation, though at a very low dose. Millimeter wave scanners are now the standard at U.S. airports.