# Dimmer switch and phase-cutting controls

> Phase-cutting dimmers chop the mains waveform and inject harmonics from a few kilohertz up to about 1 MHz onto the building wiring — the classic source of what practitioners call dirty electricity.

- Canonical URL: https://emfbase.com/emitters/dimmer-switch
- Collection: Sources & emitters
- Record id: `emitters:dimmer-switch`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/emitters/dimmer-switch
- Also known as: light dimmer, triac dimmer

## Key values

- **Category:** dirty electricity
- **Emission bands:** Harmonics 2 kHz–1 MHz
- **Environments:** home, workplace
- **Duty cycle:** Whenever the dimmed circuit is on and not at full brightness.

## Field strength by distance


## Mitigations, most effective first

- **Replace phase-cutting dimmers with plain switches, or with dimmable LED drivers designed for low conducted emissions.** — Removes the harmonic source rather than filtering its symptoms.
- **Measure conducted harmonics on the circuit before and after any filter installation.** — Plug-in filters shift and sometimes increase harmonic content; only measurement shows the net effect.

## Why no value is published at 30 cm

Assessed as conducted harmonic content on the circuit, not as a distance profile. Building-biology practice grades harmonics from 2 kHz–1 MHz more severely than the 50/60 Hz field by a factor of roughly 10–100.

## Measure with

- Dirty-electricity (line harmonics) meter
- Oscilloscope line adapter

## Related records

- [Building Biology SBM-2024 AC electric field bands](https://emfbase.com/limits/building-biology-ac-electric-bands): Sleeping-area grades with ground reference: below 1 V/m no anomaly, 1–5 weak, 5–50 strong, above 50 V/m extreme; body voltage below 10 mV is 'no anomaly'.
- [Dirty electricity](https://emfbase.com/glossary/dirty-electricity): High-frequency harmonics and transients riding on mains wiring, typically from dimmers, switch-mode supplies and inverters. Not a term used in any exposure standard.

## Sources

- `sbm-2024` Institut für Baubiologie + Nachhaltigkeit (IBN) (2024). *Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)*. https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf — ngo, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.