1 Scope

1.1 These requirements cover heat-actuated fire detectors intended for nonhazardous indoor, unconditioned areas, and outdoor locations, for use as components in automatic fire protective systems, to be installed in accordance installation in accordance with:

1. a) In Canada:

   1. 1) The National Building Code of Canada;

   2. 2) The National Fire Alarm Code of Canada;

   3. 3) The Standard for the Installation of Fire Alarm Systems, ULC-S524;

   4. 4) The Canadian Electrical Code, CSA C22.1;

2. b) In the United States:

   1. 1) The National Fire Alarm and Signaling Code, NFPA 72;

   2. 2) The National Electrical Code, NFPA 70.

Summary of Topics

This revision of ANSI/UL 521 dated October 24, 2025 includes the following changes in requirements:

– Correction to delete Section 60, Sensitivity Test Feature, per the proposal dated May 10, 2024.

– Battery Tests – Lithium Metal Type; Section 34A, 48.2.4A, 48.2.5, 48.2.5A, 54.2.1A, 54.2.1B, 67.1

– Editorial change to 57.4.2 and Annex C