Controversial airport screening machines are safe, new report shows Older generation full-body scanners deployed at the nation's airports are safe even for the most frequent travelers, according to the Department of Homeland Security's Office of the Inspector General (OIG). In a report out today, the OIG says independent tests of the machines show that a passenger would have to be screened 17,000 times a year to reach the scientific community's assessment of the annual radiation dose limit. That would be the equivalent of 47 screenings on each of the 365 days of the year. The report addresses concerns with backscatter X-ray machines. A total of 247 of them are in use at 39 airports. Click here to read the full report (PDF). "From February 2011 to June 2011, the OIG assessed the manner in which TSA inspects, maintains and operates backscatter units used in passenger screening," TSA said in a press release. The OIG found that TSA was in compliance with standards regarding radiation exposure limits and safety requirements. The backscatter machines are checked every six months and whenever a unit is moved or is subjected to any maintenance action that would affect its operation. "No accidental radiation overdoses of backscatter units have ever occurred," OIG said in the report. The report recommends, and TSA agrees, that machine operators receive more extensive training. NBC News' Pete Williams contributed to this report.