During today's NFPA Technical Meeting in Chicago, the following action has taken place on NFPA 520, Standard on Subterranean Spaces 520-1 Motion to Accept Public Comment Nos. 1 and 2 failed. NFPA 520 was passed with 0 amending motions. NFPA 520 COMPLETED. Read full coverage of the NFPA Conference & Expo on our blog.