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Standard for Heat Detectors for Fire Protective Signaling Systems

UL Revision
Standard 521, Edition 7 Edition Date: October 22, 2004 $254.00
Summary of Topics s0521_7_sum.html

Summary of Topics

This revision of ANSI/UL 521 dated July 1, 2019 is being issued to incorporate the following changes:

Modification to Table 18.1, Heat detectors, and Table 53.1, Marking

Heat Detector Color Markings

Field Programmable Heat Detector Marking

Back to Standard 521, Edition 7

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