These cameras record light that objects reflect. Recordings from these cameras show up on video screens with hotter objects looking brighter.

They are sensitive to heat, measuring temperatures down to a fraction of a degree Fahrenheit, said Andrew Sarangan, an associate professor in the University of Dayton’s electro-optics program. They can even work in the dark.

The Camera merges visual and thermal images to create a “heat picture” of a person. A pointer automatically shows the hottest area in the picture, which is usually a person’s face, mainly because it’s not covered in clothes.

However, the cameras can detect higher temperatures, but they can’t screen for swine flu itself. If someone in a hurry to catch a flight can have a higher body temperature. A fever also does not mean someone is sick with swine flu, so airports need to do further screening once they spot passengers with high temperatures.