Article 10 of the Code for the Detection of Hair Samples of Drug-related Personnel issued by the Ministry of Public Security shows that the hair samples within 3 cm of the hair root end are positive, indicating that the tested personnel have taken drugs within 6 months before the date of hair sample extraction. This is the standard for public security to collect hair for testing.

In order to standardize the detection of hair samples of drug-related personnel, fully promote the practical application of hair drug detection technology, and improve the ability of public security organs to investigate and control drug users, the Ministry of Public Security has formulated the Code for the Detection of Hair Samples of Drug-related Personnel (hereinafter referred to as the Code).

All localities are requested to accurately understand and grasp the main contents and specific requirements of the specification in combination with local work practice, and timely organize the publicity and training of the specification to ensure the smooth and orderly development of hair sample extraction, preservation, inspection and testing.

When collecting hair samples, the staff should wear disposable gloves, use medical scissors or serrated scissors to cling to the scalp surface of the person being collected, and cut off the hair at the back of the head (if enough hair cannot be extracted from the back of the head, the head closest to this part can be selected), and the length should not exceed 3 cm; Hair longer than 3 cm needs to be cut 3 cm from the root end.