Checked Baggage Explosives Screening

How hold-baggage explosives detection systems work in the U.S. and Europe

Every checked bag on a commercial flight from the United States or the European Union is screened for explosives before it is loaded. Most of that screening happens out of sight, in baggage halls behind the check-in desks, where automated explosives detection systems (EDS) — large CT scanners built into the conveyor system — inspect bags at high speed. This page explains how checked (hold) baggage screening works, what TSA and EU certification mean, who makes the machines, and why your bag sometimes comes back with an inspection notice inside.

Why checked bags are screened differently

Cabin bags are screened in front of the passenger, one at a time, by an officer looking at every image. Checked bags travel through an automated baggage handling system, often thousands per hour at a large hub, and the main threat of concern is a concealed bomb rather than knives or other prohibited items. That favours automated explosives detection with human review only when the machine is not satisfied.

In the U.S., the Aviation and Transportation Security Act of 2001 required screening of all checked baggage for explosives, a requirement TSA implemented from the end of 2002. EU rules under Regulation (EC) 300/2008 and Implementing Regulation (EU) 2015/1998 likewise require all hold baggage to be screened before loading.

The multi-level screening process

Most airports use a tiered ("multi-level") process. The names vary, but the logic is the same:

  1. Level 1 – automatic EDS scan. Every bag passes through a CT-based EDS. Algorithms analyse the 3-D image for materials whose density and composition match explosives. Most bags are cleared automatically here.
  2. Level 2 – on-screen alarm resolution. If the machine alarms, the image is sent to a screener in a remote viewing room, who examines the 3-D image and either clears the bag or sends it on.
  3. Level 3 – physical inspection. Bags that cannot be cleared on screen are diverted to an inspection area, where officers open them and use explosive trace detection and physical search.
  4. Further levels. If a threat cannot be ruled out, the bag is handled as a suspect item and specialist bomb-disposal procedures take over.

Smaller airports may use standalone EDS machines or ETD-based screening instead of a fully integrated in-line system.

How a checked-baggage EDS works

Modern hold-baggage EDS machines are computed tomography scanners similar in principle to checkpoint CT, but with larger tunnels and higher belt speeds to keep up with baggage-system throughput. Many add dual-energy or multi-energy data so the system can estimate both density and effective atomic number for each object. The detection algorithm segments the bag into objects, measures their properties and alarms on those that fall within threat ranges. Some older systems combine conventional multi-view X-ray with a CT stage for alarmed bags.

TSA certification and qualified equipment

In the U.S., TSA certifies EDS equipment for checked baggage after laboratory testing against classified detection standards, and then tests it operationally. TSA publishes a list of certified and qualified screening technologies by vendor and model, including EDS for checked baggage and air cargo. Airports and airlines working on new or upgraded baggage systems follow TSA's Planning Guidelines and Design Standards for checked baggage inspection systems.

Manufacturers with TSA-certified checked-baggage EDS include Smiths Detection (CTX and HI-SCAN XCT families), Leidos (eXaminer family, from its 2020 acquisition of L3 Security & Detection Systems), Analogic and Rapiscan Systems. The exact list changes as models are certified and retired, so always check the current TSA list rather than a vendor brochure.

Europe: ECAC Standard 3

In Europe, hold-baggage EDS is tested through the ECAC Common Evaluation Process against graded standards. The current requirement is Standard 3, which demands detection of a wider range of explosives in smaller quantities than the older Standards 1 and 2 — in practice, CT-based equipment. The EU originally required Standard 3 equipment across most airports by 2020 (with the UK aiming for 2018), but deadlines were extended, notably during the COVID-19 pandemic.

Implementing Regulation (EU) 2021/255 sets a progression for newly installed equipment: equipment installed between September 2014 and August 2022 must meet at least Standard 3; equipment installed from 1 September 2022 to 31 August 2026 must meet at least Standard 3.1; and equipment installed from 1 September 2026 must meet at least Standard 3.2.

Why was my checked bag opened?

If the EDS alarms and the on-screen review cannot clear it, the bag is opened. In the U.S., TSA places a Notice of Baggage Inspection inside to tell you it was physically inspected. Common reasons include:

  • Dense items packed tightly together, such as stacks of books, tins or electronics.
  • Organic materials whose density resembles explosives — some foods, cheeses, chocolate blocks, liquids and powders.
  • Items the image cannot separate clearly, such as cables wrapped around batteries.

To avoid a cut lock in the U.S., use a TSA-recognised lock or leave the bag unlocked. Spreading out dense items and packing electronics loosely also helps.

Common myths

  • "Checked baggage X-ray will ruin my film." High-powered EDS scanners can fog undeveloped film, which is why film belongs in your carry-on — see film, electronics and food.
  • "Every bag is opened." No; the vast majority are cleared automatically or on screen.
  • "The machines only look for guns." The primary target for checked baggage is explosives; prohibited-item checks are a secondary benefit.

For carry-on screening see airport security screening; for the regulatory background see regulations.

Frequently asked questions

How are checked bags screened for explosives?

They pass through an automated explosives detection system, usually a CT scanner built into the baggage conveyor. Bags that alarm are reviewed on screen by an officer, and those that still cannot be cleared are opened and checked with explosive trace detection.

Which companies make TSA-certified checked baggage scanners?

Certified EDS manufacturers include Smiths Detection, Leidos, Analogic and Rapiscan Systems. TSA publishes the current list of certified and qualified models.

What is ECAC Standard 3?

It is the European performance standard for hold-baggage explosives detection systems, tested through the ECAC Common Evaluation Process. It requires detection of more explosive types and smaller quantities than earlier standards and generally requires CT technology.

Why did TSA open my bag?

Usually because the EDS image could not be cleared on screen — often due to dense or tightly packed items or organic materials that resemble explosives in density. TSA leaves a Notice of Baggage Inspection in bags it opens.

Sources and further reading

Note: This is an independent educational reference, not an official TSA, EU or ICAO publication. Screening rules change; always check the operator or regulator for current requirements. See our full disclaimer.

Last reviewed on 2026-10-04.