different instances is extremely alarming. and i would say even dangerous. >> i am putting a detonator into the plastic explosive. >> reporter: cnn was there in 2008 for a similar covert operation. that time it was tsa testing its own officers. >> okay check. >> reporter: at the checkpoint the tester is wanted and patted down where the fake explosive device is concealed. but the screener missed it. it's not until the tester lifts his shirt up. >> oh i see it now. >> reporter: the department of homeland security says it, quote, immediately directed tsa to implement a series of action several of which are now in place. >> is it the technology that's failing or is it the screeners themselveses not following proper protocol? if tsa's screening equipment is failing in not doing the job, that's a larger systemic issue that tsa needs to address.