# Shielded mains cable and shielded conduit

> Screened NYM-style cable or metal conduit with a grounded screen removes the AC electric field at source, and is the correct fix during construction or rewiring.

- Canonical URL: https://emfbase.com/shielding/shielded-cable
- Collection: Shielding & remediation
- Record id: `shielding:shielding-shielded-cable`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/shielding/shielded-cable
- Also known as: screened cable, shielded romex, metal conduit

## Key values

- **Form:** paneling
- **Targets:** elf electric
- **Grounding required:** Yes — ungrounded installation can make things worse

## Failure modes

- The screen must be bonded to protective earth at one defined point; an unbonded screen provides no benefit
- Does not reduce magnetic fields — those come from current, not from the conductor's field
- Only effective for the runs actually replaced; a single unshielded lamp flex can dominate the room again

## Related records

- [Bedroom wiring AC electric field](https://emfbase.com/emitters/bedroom-wiring-electric-field): Live conductors in walls and in lamp flex create a power-frequency electric field that couples to the body whether or not any current flows; building biology grades below 1 V/m with ground reference as 'no anomaly'.
- [Demand switch (Netzfreischalter)](https://emfbase.com/shielding/demand-switch): A relay in the consumer unit that de-energises a circuit when no load is drawing current and re-energises it when a switch is thrown, eliminating the bedroom AC electric field overnight.

## 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.