UL 521

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

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

Sourceosha.gov

Verified2026-08-10

Review by2026-12-08

DatasetWhich OSHA NRTL is recognized for which test standard: all 21 labs' scopes of recognition, cross-referenced

What the source says

UL 521 | Heat Detectors for Fire Protective Signaling Systems |

— osha.gov, retrieved 2026-08-10

Source

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

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.