In pictures: North Korea hydrogen bomb test

A lab employee from the Korea Institute of Nuclear Safety's regional office in Gangneung, east of Seoul, checks for radioactive traces in the air, in Gangneung, soon after North Korea announced it successfully conducted a hydrogen bomb test. The office in Gangneung is the closest one to the site of the North's claimed test. Officials said it will take three to four days to analyze air samples in detail for any traces of radioactivity, the Yonhap news agency reported

EPA