The detectors were installed at the Saddledome during the Olympic break by the Calgary Flames organization, as part of a National Hockey League mandated security enhancement. They were put to use prior to the Flames' 2-0 loss to the Los Angeles Kings.
When fans entered the Scotiabank Saddledome, they received a pamphlet with the following message.
"The Scotiabank Saddledome has been implementing enhanced guest security and safety measures over the course of the 2013-14 season. The next phase of the enhancement is the installation of walk through metal detectors at all main entry points to the venue. The installation is still in progress with full operation expected over the next month. These measures are consistent with those in effect at other NHL venues and most large public assembly venues throughout North America....Guests are discouraged from bringing bags or items requiring inspection into the venue as our goal is to expedite entry as much as possible. Prohibited items that are discovered during security inspections must be either returned to the owner’s vehicle or discarded. Unlawful items that are discovered during security inspections are subject to confiscation. Please arrive early and open coats, jackets, purses and/or bags before approaching the metal detectors. This will assist with an expedited entry into the venue."
In 2013, there was a bombing at the Boston Marathon, so it is not totally surprising the NHL has put these added security measures in place to help protect the safety of spectators.