Fire Service Ground Ladders (9th Edition)-All Chapter Numbers

1 1/4. inches. in diameter at the center. Swell center rungs (rungs thicker at the center) must be 1 1/4. inches. in diameter at the center, however, they may taper to . 1 1/8. inches. at the ends. NFPA 1931. requires rungs on wood ladders be spaced from . 12 to 14 inches. on center, plus or minus . 1/8. inch. NFPA. 1931. requires all ... ................
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