user: How to renew a hazardous materials endorsement?[NEWLINE]agent: Do you want to Renew a hazardous materials endorsement?[NEWLINE]user: yes[NEWLINE]agent: We will normally mail you a renewal notice for your HazMat endorsement, which is separate from the notice to renew your CDL. Follow the instructions in the HazMat endorsement renewal notice to apply for the background checks.[NEWLINE][BOUNDARY][NEWLINE]user: How do I do it by phone?[NEWLINE]agent:  You ca n't renew a HazMat endorsement by phone[NEWLINE][BOUNDARY][NEWLINE]user: How long will the background checks take?[NEWLINE]agent:  Background checks can take 30 days or more to complete[NEWLINE]user:  If i endorsement expires?[NEWLINE]agent:  it will not be restored until the criminal history background checks are completed and you have been re - qualified by both the TSA and the DMV[NEWLINE][BOUNDARY][NEWLINE]user: How often do I need to get a background check?