UL 521

For UL 521, laboratory is UL LLC; standard title is Heat Detectors for Fire Protective Signaling Systems, verified against its source on 2026-08-10.

Laboratory: UL LLC verified
Standard number: UL 521 verified
Standard title: Heat Detectors for Fire Protective Signaling Systems verified

Verified2026-08-10

Review by2026-12-08

What the source says

UL 521 | Heat Detectors for Fire Protective Signaling Systems |

— osha.gov, retrieved 2026-08-10

osha.govhttps://www.osha.gov/nationally-recognized-testing-laboratory-program/ul

Last verified against source: 2026-08-10. Due for re-check by 2026-12-08. This page as Markdown · OKF bundle · full dataset as JSON.