It has been understood for some time that facilities like Stadiums, Arenas, and Conference Halls are prime terrorist targets because so many people are gathered in one place at the same time. In the US alone, there are 218 large stadiums ranging from 20,000 to 110,000 in capacity with an average of 50,000 capacity. There are 350 indoor arenas in the US averaging 12,000 capacity and ranging from 5,000 to 23,000 capacity. In general since these kinds of gatherings have specific start and end times for events, and there are many entrances/exits. Pedestrian traffic rates coming and going can be substantial. Where there are security checkpoints today, they typically involve a manual search of packages and sometimes metal detection archways and x-ray machines. These will not stop a determined attacker. The solution is placing Barbecan Portals at all entrances.
Even outdoor gatherings can be noticeably safer with (portable) Barbecan portals used at entrances to closed-off areas. Such a deployment would have prevented the Boston Marathon bombing by detecting the pressure cookers and shrapnel used for the bombs. Similarly, large gatherings like New Year's Eve in Times Square and other cities can have increased security levels with portable Barbecan portal deployments. Large outdoor marketplaces are prevalent around the world - especially in Asia and the Middle East. Barbecan portals can also make these safer.