Heat Sensitive Security Systems

While much of the technology in movies seems like science fiction, a good number of the interesting devices we see in films actually exist and, in a simpler form, are used every day. For example, the movie Mission: Impossible featured a heat-sensitive security system designed to sense the slightest changes in temperature. In a simplified form, the same technology is already at work in passive infrared systems and more sophisticated heat-sensitive alarms.

What Is Passive Infrared?

Passive infrared refers to sensors that can pick up changes in heat in an environment. Every object gives off some degree of heat in the form of infrared light. This light is not visible to the naked eye but can be picked up by infrared sensors, such as those used in IR glasses or cameras.

A passive infrared system relies on a core of pyroelectric material that responds to changes in heat. Normally, IR systems utilize gallium nitride, cesium nitrate, various fluorides or cobalt to absorb heat and relay information to switches.

This type of sensor is commonly used in motion-detecting lights. The name is a misnomer, for the lights do not sense motion as much as they do changes in temperature in their vicinity. Most of these lights are calibrated so that they do not react to every stray breeze but instead to solid changes in infrared activity. However, the motion does not necessarily have to be made by a person; even a small animal may set of motion-sensitive lights or alarms.

Passive infrared systems have been on the market for some time and have been adapted to cameras, lights and other security devices. They are relatively inexpensive; an outdoor motion-sensitive IR light can cost as little as $10.

Other Types of Heat Detectors

While IR motion-sensitivity is the most common application of heat-detecting security devices, there are other methods of using heat to trigger certain actions by a system. For example, many smoke detectors now also feature heat detectors. If the temperature in a room rises above a certain level, whether there is smoke or not, the alarm will go off.

Very sophisticated heat-seeking equipment is also used by the government to allow missiles to find targets. However, this technology is not available to the general public and some of the information about how these weapons work is classified.

One interesting way heat technology is being used for security is on paper. Heat-sensitive paper allows a user to rub his or her thumb across the paper, raising the temperature to 88 degrees Fahrenheit. If the paper does not change, the user knows that the instrument is forged or copied. Banks are beginning to turn to this use of heat security, and at some point paper money may use it as well.

Heat-sensitive technology is nothing new, but technological advances have made it possible for this security to be used in much smaller spaces and for the devices to become much more sensitive. In the future, expect to see thumb-sized heat-sensitive strips that control access to buildings as well as heat-sensitive identification technology for computers and other protected items. There may also be development of much stronger and more sensitive heat-change alarms in museums, art galleries, jewelry stores and other places where valuables are kept.