gauss (gauss)

Gauss (symbol: G) is the CGS unit of magnetic flux density — that is, magnetic-field strength per unit area. One gauss equals 100 microtesla, or equivalently one tesla equals 10,000 gauss. The unit is named after the 19th-century mathematician Carl Friedrich Gauss and remains the practical engineering unit for specifying degausser performance and magnetic-separator field strength in the recycling and data-destruction industries, even though the modern SI unit is the tesla.

Reference values for context: Earth's magnetic field at the surface is 0.25-0.65 gauss depending on latitude. A typical refrigerator magnet produces 50-200 gauss at the surface. The NdFeB voice-coil magnet inside a hard disk drive produces 3,000-10,000 gauss at the air gap. An MRI scanner for medical imaging operates at 1.5-3.0 tesla, equivalent to 15,000-30,000 gauss. A modern NIST-compliant HDD degausser produces a peak field of 15,000-22,000 gauss at the centre of its chamber for the millisecond-to-second duration of the erasure pulse.

Why gauss matters for data destruction: Every magnetic storage medium has a characteristic coercivity — the magnetic-field strength required to flip its magnetic polarity. Modern HDD platters use high-coercivity perpendicular-recording films with coercivity of 4,000-5,500 oersted (an oersted is the CGS unit of magnetic-field intensity, numerically equal to gauss in air). NIST guidance specifies that a degausser must exceed the media coercivity by at least a 2:1 margin to guarantee complete data destruction; modern degaussers therefore target 15,000-20,000 gauss to safely erase media with 5,000-oersted coercivity. Older degaussers rated at 5,000-8,000 gauss were sufficient for legacy HDDs but cannot erase modern high-density drives — a frequent and undetected compliance gap at Indian e-waste plants that have not upgraded equipment.

Verification and certification: Degausser performance is measured by a Gauss meter (or magnetometer) inserted into the chamber during commissioning and periodic re-verification. NIST SP 800-88 Rev. 1 requires verification at intervals specified by the degausser manufacturer, typically every 12 months. Indian recyclers serving GDPR-regulated European clients or HIPAA-regulated US healthcare clients must maintain dated Gauss-meter calibration records to demonstrate field strength continuously meets the certified specification. Failure mode: degaussers can lose 10-20% of peak field strength over 3-5 years as capacitors age, silently dropping below the certified specification while still producing authentic-looking destruction reports.