Some workers may carry items regularly for protection and were not accustomed to being screened on their way to work, according to the airport.
"Part of it may be education," Southwell said. The airport notifies the worker's employer when such a prohibited item is found, he said.
Before this year, most those who work in secure areas of the world's busiest airport airport were not screened.
The security gap at Atlanta's airport and other airports around the country drew scrutiny late last year, with the discovery of a gun smuggling ring at Hartsfield-Jackson. That triggered a federal review of airport access control.
Amid concerns about the possibility of an "inside threat" and gaps in security screening of airport workers, Hartsfield-Jackson plans to open another security checkpoint for employees. More than 40,000 people work in secure areas of the airport.
The Atlanta airport in September opened a three-lane checkpoint on the mezzanine level of the domestic terminal below the main floor of the airport to screen airport workers.
With plans to increase screening to include Delta Air Lines workers, Southwell said he hopes to open in 2017 a six-lane employee screening checkpoint where the current American Airlines baggage claim sits on the lower level of the domestic terminal.
American Airlines baggage claim would be moved to the main level, where there is available space, according to Southwell.