# IEEE C37.21 — Which OSHA-recognized labs (NRTLs) can certify to a given test standard

For IEEE C37.21, standard title is Control Switchboards; nrtl is CSA; laboratory is CSA Group Testing and Certification Inc; status is currently recognized, recorded from its source on 2026-08-10.

- **Test standard:** IEEE C37.21 _(verified: appears in the quote below)_
- **Standard title:** Control Switchboards _(verified: appears in the quote below)_
- **NRTL:** CSA _(verified: appears in the quote below)_
- **Laboratory:** CSA Group Testing and Certification Inc. _(verified: appears in the quote below)_
- **Status:** currently recognized _(our reading, not quoted from the source)_

## What the source says

> IEEE C37.21 | Control Switchboards |

## Source

- https://www.osha.gov/nationally-recognized-testing-laboratory-program/csa

Last verified: 2026-08-10. Review by: 2026-11-08.
Part of [Which OSHA-recognized labs (NRTLs) can certify to a given test standard](https://referencesource.org/nrtl-recognized-test-standards/).