Subway will be soon adding an extra measure of security to protect its tens of thousands of franchise locations around the country, reports WATE. Instead of extra alarms or bells, the new security system, manufactured by SelectDNA actually sprays intruders, robbers, or other criminals, with a chemical that marks offenders as they try to exit the shop, reports Fox News. 

A box filled with the dye unique to a particular store, called DNA, is kept above entryways. In the event or a crime, a mechanism will release the traceable spray onto the offender as he or she tries to exit. The dye glows when exposed to a blacklight, can't be washed off and stays on for up to seven weeks.

Subway says they will hang new signs in sandwich store windows to deter potential criminals from committing crimes within.

 http://www.foxnews.com/leisure/2015/05/12/subway-to-start-spraying-thieves-with-tracking-liquid-in-new-security-measure/