Sunday, February 8, 2009

Apple #369: Anti-Theft Dye Packs

Daily Apple reader Tim recently asked,

Hey, Daily Apple, any chance you'll blog soon about the exploding dye packs that bank tellers slip in with the cash when a bank gets held up?

Chances are 100%. Tim, I'm answering your question right now.

In case you're nervous about this topic -- I sort of was -- there is a lot of information publicly available about these dye packs. I haven't done anything covert or weird or super-sleuthy to get this information. You'll also notice I haven't revealed anything about how to disable the dye packs or how to remove the dye from one's hands or clothing. So I doubt I've given any would-be thieves that much help.

And by the way, just to make the pronoun thing easier, I'm going to refer to the thieves as male. Sometimes the bank robbers are female (one woman dressed up like a witch to rob a bank), but the majority of the time, the thieves are male.

  • Most of the dye packs used by banks in the United States are made by a company called 3SI. The brand name of the packs they make is SecurityPac. So that's what I'll be describing here.
  • I thought maybe they would be little packages that the teller had to be all cagey about slipping into the thief's bag, but it's actually more ingenious than that.
  • 3SI takes a stack of bills -- usually 20s -- and hollows out a space in the middle of the stack. In there they hide one of the dye packs.

SecurityPac dye pack tucked into a hollowed-out stack of 20s. There would also be a second half of the stack of 20s that closes over the dye pack. Similar devices are also designed for use in vaults and in ATM machines.
(Photo from the FBI)

  • I don't know when that photo was taken, but apparently the dye packs currently in use are flexible enough that a thief can't tell that the pack is in there by squeezing or bending a stack of bills.
  • There's actually a lot of technology hiding in that little secret dye pack. First, there's a radio receiver on a circuit board. When the thief exits the bank carrying his sack of bills, a radio transmitter on the bank's door frame communicates with the little receiver in the dye pack and essentially turns on the circuit board.
  • But the thing doesn't go into action immediately. There's a 10-second delay, which allows the thief enough time to get away from any innocent bystanders, and also maybe to get in his getaway car and thus mark the vehicle as well.
  • After the 10 seconds has passed, there's a little pop and the dye pack explodes, activating any or all of the following:
  1. a great cloud of red dye
  2. a stream of tear gas
  3. a fire
  • First, the dye. It's very red. Its chemical name is 1-methylaminoanthraquinone, or MAAQ for short. It's been used by the military in colored smoke grenades with a slightly different chemical composition, and it's also been used to dye the lenses that cover car tail lights. When this dye gets on something, it sticks. Some thieves have tried to use bleach to get it off their hands and clothes and off the money they've stolen, but even that doesn't work. The forensics people can detect the dye and the bleach.

Stack of 20s stained with the MAAQ, and the dye pack having been ejected nearby.
(Photo sourced from Wall$treet Fighter)

  • Included with the dye are potassium chlorate, which is an explosive and is used in fireworks fuses. This is basically the ignition source which makes the dye explode. Also included is confectioner's sugar. That's what makes the dye puff everywhere.

Cloud of red dye, exploding from a dye pack.
(Photo by 3SI, sourced from the Center for Problem-Oriented Policing)

  • As for the tear gas, it's your basic CS tear gas which is used by the police for riot control, and is in those personal defense tear gas sprays that you can buy. Standard, noxious stuff.
  • Now for the fire. Extending from the circuit board is a "squib" or something like a fuse, which leads to a pouch containing a chemical mixture that 3SI doesn't want disclosed. That mixture gets heated to 400 degrees F. That's hot enough to start burning the money and, more importantly, to keep the thief from grabbing the offending money stack and getting rid of it or the dye pack.
  • The whole idea is that the combination of red dye, tear gas, and fire will make the thief drop all the money and run. The dye on his hands will serve as a finger of guilt so that it will be easy for police to identify the thief even after he's left the scene.

The result that 3SI envisions
(Photo from 3SI Security Systems)

  • But you can probably spot some loopholes here. They're assuming the thief will drop all the money, not just the one bundle that's spewing the nastiness. They're also assuming that someone will spot the thief with red dye all over his hands and call the police. In fact, even though the dye is really hard to remove, some thieves do still get away with it. Or at least, if they don't get away with the money, they don't get caught.
  • In 2002, 3SI reported that their dye packs were used in 1,078 robberies. They say that 72% of the stolen cash was recovered, and 25% of the robbers were arrested. Though that's a good percentage of money returned, the number of arrests seems pretty low.
  • So 3SI and other companies have loaded up the dye packs with still more gems. These things have already been deployed in some dye packs in the United States and Europe:
  1. siren that screams when activated
  2. GPS tracking device
  3. DNA tagging, which marks the criminal with a very precise identifier of the location attacked.
  • Something else that has gone wrong in the plan is that sometimes a teller has mistakenly given a stack of bills with a dye pack in it to an innocent customer. One guy in Seattle whom this happened to had to be taken to a hospital, get washed in a chemical-removing shower, and be treated for second-degree burns.
  • In most cases where these accidents have happened, the bank tellers and managers don't explain to the press what went wrong or who was at fault, mainly because they're too embarrassed to talk about it.
  • One guy who works for another manufacturer of dye packs said that the tellers are supposed to keep the dye pack stacks of bills on a magnetic plate. This keeps the radio signal on the door frame from setting off the pack inside the bank. This guy said that this magnetic plate makes "Accidental activation a thing of the past." Except that was in 1991 and a lot of those accidental activations occurred within the past five years.
  • In spite of such errors and flaws, sometimes it all does go as planned. Remember that woman I mentioned at the outset who dressed up as a witch and held up a bank? A dye pack exploded on her. Even though she ditched the witch's hat and the $2,000 she'd stolen, she was arrested, convicted, and sentenced to 13 years in prison. She had actually committed several other hold-ups. Police estimate she had stolen $11,500 over the course of her robbing career.

She looks like a friendly witch, doesn't she? Er, witch and habitual bank robber, that is.
(Photo from KIROTV, sourced from

Howstuffworks, I've heard of bank robbers being foiled by a "dye pack" put in their money stash. What is a "dye pack?"
Pamela C. Reynolds, FBI Laboratory, Forensic Science Communications, "Analysis of Bank Dye Evidence and the Challenges of Daubert Hearings," January 2008
US Patent 5485143, Security dye pack having flexible heat-resistant chemical pouch (abstract)
US Patent 6552550, 3SI, Flexible smoke generator
3SI North America, SecurityPac,
3SI Europe, SecurityPac, Unique DNA Tag Deters Attacks
Mary Pifer of 3SI Security Systems, Credit Union Magazine, Dye packs deny cash prize to robbers, September 2003
Credit Union Resources, ScreamerPac
Lester Haines, "DNA 'tagging' powder combats unwanted intrusions," The Register, July 25, 2005
Credit Union National Association, Security Solutions for Cash Protection
James M. Egan et al., "Bank Security Dye Packs: Synthesis, Isolation, and Characterization of Chlorinated Products of Bleached 1-(methylamino)anthraquinone," Journal of Forensic Sciences, November 8, 2006.
"Caught Red-Handed!" Bankers' Hotline, June 1991, sourced from
Sara Jean Green, "Dye-pack explosion injures man at bank," The Seattle Times, March 4, 2005
AP, "Woman In Witch Costume Robs Washington Bank," November 1, 2005
Alan Wagmeister, "Witchy Bank Robber Gets Jail Sentence," Digitriad (Triad, NC), May 4, 2006


  1. Very interesting read!

  2. Is it practicle to use these dye packs in a home setting? In order to catch a thief?

  3. Anonymous, I doubt it would be practical to use these in your home. First of all, I'm not sure where a homeowner could buy such things and I have the feeling the cost would be higher than you'd want to pay. Second, you'd have to rig your doorways and windows so they worked with the dye packs. Thirdly, do you keep stacks of cash around your house? If not and it's something else you're worried about someone stealing, would you really want unremovable red dye to be sprayed all over it?

    I'd say you're better off using some other system that is designed for home security and personal objects.


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