I've heard of bank robbers being foiled by a "dye pack" put in their money stash. What is a "dye pack"?

In a typical bank robbery, the robber hands a note to the bank teller listing his demands, usually instructing the teller to put money in a bag or other object. The dye pack device was invented as a way to non-violently render a bank robbery pointless by permanently staining the stolen money a bright red color, alerting everyone to the fact that the money being passed to them is stolen.

The dye pack used in over 75 percent of banks in the United States is called the "SecurityPac," made by ICI Security Systems. A dye pack consists of a stack of real bills, usually of $10 or $20 denominations, with the dye device stuck in the middle of the stack. In the past, the device itself was made of a rigid plastic and was quite detectable to the skilled criminal. Today, however, new technology has allowed the dye to be housed in a thin, flexible package, making a dye pack virtually indistinguishable from a regular stack of money.

Bank tellers have several of these packs near their station at all times. A pack is put in "safe" mode by attaching it to a special magnetic plate. During a robbery, a teller tries to slip one of the dye packs into the money bag without the thief noticing. While the thief is still inside the bank, the dye pack remains dormant. Within the dye package is a small radio receiver that is activated when the pack is removed from the magnetic plate. A small radio transmitter is mounted inside or near the door frame of all entrances of the bank. Once the dye pack passes through the door and receives the specific radio frequency signal, it activates. The dye pack is usually set on a timer of 10 seconds or longer so that the criminal is either in his getaway car or running a good distance from the bank before the package explodes.

When the dye pack explodes, it releases an aerosol of red smoke, red dye (1-methylamino-anthraquinone) and, in some cases, tear gas. When these chemical reactions take place, the package burns at a temperature of about 400 degrees Fahrenheit (204 degrees Celsius), discouraging any attempts to remove the device from the bag. (Further details of the chemical activation are "classified.") Typically, the explosion of the dye pack compels the thief to throw the bag, so the bank gets its money back. In addition, the red dye frequently stains the thief's clothes and/or hands, making identification of the suspect quite easy.

To date, the "SecurityPac" has helped to recover nearly $20 million and to apprehend about 2,500 criminals.

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Dye Pack FAQ

Do banks still use dye packs?

Over 75 percent of banks in the United States still use dye packs. In the past, they were made of plastic and were quite detectable to criminals, but today, technology has made them practically indistinguishable. The dye is housed in a thin, flexible package that makes it look like a regular stack of money.

What is the point of a dye pack?

A dye pack contains a stack of real bills, usually of $10 or $20 denominations, along with the dye device hidden in the middle of the stack. It is a radio-controlled device used by banks to prevent robbery and make stolen cash unusable by making it permanently stained with dye after being illegally taken out of the bank.

How does a dye pack go off?

A dye pack is in "safe" mode as long as it is attached to a special magnetic plate. During a robbery, a teller will slip one of the dye packs into the money bag. While the stack of bills is inside the bank, the dye pack remains inactive. The dye package also has a small radio receiver that activates when the pack is removed from the magnetic plate. This receiver communicates with a small radio transmitter mounted inside the bank. Once a thief takes the money bag with the dye pack out of the bank, the pack receives a specific radio frequency signal and goes off, leaving the cash stained.

What color are bank dye packs?

Bank dye packs are usually red. They are a great way to non-violently foil a bank robbery by permanently staining the stolen money bright red, alerting anyone who sees it that itâ€™s stolen.

What happens when a dye pack explodes?

When the dye pack explodes, it releases an aerosol of red smoke, red dye and sometimes, tear gas. The dye pack burns at 400 degrees Fahrenheit, preventing any attempts to remove the device from the bag. Usually, the explosion of the dye pack makes the thief throw away the bag, rendering the robbery pointless. The red dye can also stain the thief's clothes and hands, which makes identification of the suspect easier.