X-ray inspection system displays different types of substances in different colors. It reflects organic substances as orange, inorganic substances as blue and mixed substances as green.

Excellent question! The colors on airport scanner displays (both for carry-on baggage and full-body scanners) are a simplified code to help security officers quickly identify potential threats. The meaning is slightly different for the two main types of scanners.

1. Carry-On Baggage Scanners (X-Ray Machines for Bags)

These are the machines your suitcase or backpack goes through on the conveyor belt. The colors represent the density and atomic number of the materials inside.

• Orange/Red/Brown: Typically indicates organic materials. These are mid-density, mid-atomic number items.

  • Examples: Food, paper, plastics, explosives, drugs, wood, clothing, water.
  • Why it’s key: Since most explosives and narcotics are organic, these items are highlighted for closer inspection.

• Blue/Green: Indicates metallic, dense, or high-atomic number materials.

  • Examples: Metals (guns, knives, batteries, coins), glass, bone, salt.
  • Denser metals like steel will appear darker blue, while lighter metals like aluminum may appear greener.

• Black: Represents the least dense areas or empty space that the X-rays pass through easily.

  • Examples: The empty cavity of a bag, air, or very low-density materials.

How Security Uses It: An officer looks for anomalies—for example, a dense blue block (a battery) inside an orange mass (clothing in a suitcase) is normal. But an organic (orange) mass with wires (thin blue lines) attached in an unusual shape would require the bag to be searched.

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