01A retired drive is a breach waiting to happen
Decommissioning is the one stage of the lifecycle where the asset is worth little but the data on it is worth everything.
A drive that leaves your estate intact (sold, recycled or simply skipped) is an uncontrolled copy of your data in someone else's hands. Studies of second-hand drives routinely recover live personal and corporate data from equipment that was “wiped.”
It is a legal duty
UK GDPR Article 32 and the Data Protection Act 2018 require you to keep personal data secure until it is irretrievably destroyed. Failure is a reportable breach with regulatory and financial consequences.
“Wiped” often is not
A quick format or delete leaves data fully recoverable. Even a single overwrite can be insufficient on some media, and SSDs hide data in spare cells a standard wipe never touches.
Disposal is regulated too
The WEEE Regulations govern how electronic equipment is recycled. Dumping equipment is not just a data risk; it is an environmental compliance failure.
The gap is the handover
Most exposure happens between your rack and the destruction: untracked transport, no asset register, no certificate. Without an unbroken chain of custody you cannot prove anything was destroyed at all.
02Clear, purge or destroy
The reference framework is NIST SP 800-88 Rev. 1, which defines three levels of sanitisation.
Which you need depends on the sensitivity of the data and whether the drive will be reused or has reached end of life.
Logical wipe, drive reusable
Overwrite the addressable storage (for example a verified multi-pass erase). Fine for low or moderate-sensitivity data on a drive you intend to redeploy or resell. It must be verified, and it does not reach hidden or remapped areas.
Reuse: yes
Stronger, resists lab recovery
Cryptographic erase (destroying the encryption key) or degaussing. Degaussing works on magnetic HDDs only; it does nothing to an SSD. The right choice when you need high assurance but may still reuse or recycle the media.
Reuse: possible
Physical, end of life
Shredding, disintegration, pulverising, incineration or melting. The only route for the most sensitive data and for media that cannot be reliably purged (most SSDs). Afterwards the device is unusable, which is the point.
Reuse: no
NIST SP 800-88r2 (in draft) defers the detailed technique list to IEEE 2883-2022, the current sanitisation standard, and warns that shredding may not sufficiently sanitise modern SSDs unless the particle size meets the defined threshold. That threshold is the detail most often got wrong.
03Shred sizes: HDDs and SSDs
Not all shredding is equal, and the most common, and most dangerous, mistake is shredding SSDs at hard-drive sizes.
A hard drive stores data magnetically across large platters, so a coarse shred destroys it. An SSD stores data in small NAND flash chips; a fragment a few millimetres across can hold an intact chip, and therefore recoverable data. SSDs must be shredded far finer.
Hard drives (HDD)
NSA/CSS requires magnetic hard drives to be shredded to particles of 6 mm or smaller for TOP SECRET media. Degaussing first is good practice.
SSDs and flash
NSA/CSS requires SSDs and flash media to be shredded to 2 mm or smaller, verified under a microscope. A standard HDD shredder will not achieve this.
Interactive / Particle sizes to scale
What each standard leaves behind
Pick a standard to cut the same 40 × 40 mm piece of media to its maximum particle size, drawn to scale.
NSA/CSS
DIN 66399, hard drives (H)
DIN 66399, electronic (E)
NSA/CSS, hard drives
36mm² max particle
The highest-assurance size for magnetic hard drives. Too coarse for SSDs: a fragment this size can hold an intact flash chip.
Particles are drawn as squares of the maximum permitted area; real shred is irregular. DIN 66399 is published internationally as ISO/IEC 21964.
| Media | NSA/CSS (highest assurance) | DIN 66399 / ISO 21964, by security level |
|---|---|---|
| Hard drive (H, magnetic) | 6 mm particle or smaller | H-5 up to 320 mm², H-6 up to 10 mm², H-7 up to 5 mm² |
| SSD, flash, chips (E, electronic) | 2 mm particle or smaller | E-3 up to 160 mm², E-6 up to 1 mm², E-7 up to 0.5 mm² |
DIN 66399 (now standardised globally as ISO/IEC 21964) runs from level 1 (low) to 7 (top secret) and uses separate classes for magnetic hard drives (H) and electronic and flash media (E), precisely because the safe particle size differs by an order of magnitude. A higher level means a smaller particle and a lower reconstruction risk.
The types of physical destruction
Shredding
Mechanical cutting to a defined particle size. The workhorse, but the size must match the media (see above).
Disintegration and pulverising
Repeated cutting through a mesh to a very fine, uniform particle. This is how the smallest (2 mm) SSD sizes are achieved.
Degaussing
A powerful magnetic field that erases magnetic media. Effective on HDDs and tape; useless on SSDs, because flash is not magnetic.
Crushing and piercing
Deforms a drive so it will not spin up. Data can survive on the platter or chips: fine as a deterrent, not as certified destruction.
04Standards and UK regulations
“Securely destroyed” is not a feeling. It is a set of standards you can point an auditor or regulator at.
NIST SP 800-88 and IEEE 2883
The international reference for sanitisation methods (Clear, Purge, Destroy), with IEEE 2883-2022 now defining the approved techniques and particle-size thresholds.
DIN 66399 / ISO/IEC 21964
The destruction standard with seven security levels and per-media particle sizes: what reputable shredding is specified against.
NSA/CSS EPL
The strictest physical-destruction benchmark (the 6 mm and 2 mm figures). Equipment is tested and listed by the NSA for classified media.
UK GDPR and DPA 2018
Article 32 mandates secure deletion of personal data: the legal duty that sits behind every destruction certificate.
WEEE Regulations
Govern the environmentally compliant recycling of the electronic remains once the data is destroyed.
ADISA and NCSC
ADISA's ICT Asset Recovery Standard 8.0 is an ICO-approved UK GDPR certification; NCSC's CAS-S scheme covers destruction of classified government data. Also look for ISO 27001 and NAID AAA.
05Chain of custody, end to end
Certified destruction is only as good as the chain of custody around it.
The defensible process is the same whether destruction happens on site or at a facility:
- 01
Inventory
Every asset logged by serial number before it moves, so you know exactly what must be accounted for.
- 02
Secure transport
Tracked, sealed, GPS-monitored movement, or destruction on site with witnesses to avoid transport risk entirely.
- 03
Destroy to standard
The right method and particle size for each media type (6 mm HDD, 2 mm SSD), to the level your data sensitivity requires.
- 04
Certificate per item
An item-by-item certificate of destruction tied to each serial number: your audit-proof evidence.
- 05
WEEE recycling
Compliant recycling of the destroyed remains, with environmental documentation.
- 06
Audit trail
Records retained, typically for six years, so you can evidence compliance long after the equipment has gone.
06How Optronix helps
Decommissioning is the final stage of the data centre lifecycle, the bookend to choosing and building a facility, and the one where a missed certificate becomes a breach.
We run it as a controlled project, on site or off, across the UK, Europe and worldwide.
- 01
Audit and inventory
We survey and serial-log the estate to be retired, so nothing is unaccounted for.
- 02
On-site or certified off-site destruction
Witnessed destruction in your facility, or through ADISA or ISO 27001-certified partners, to the right standard and particle size for each media type.
- 03
Full chain of custody
Tracked handling and item-by-item certificates of destruction tied to every serial number.
- 04
WEEE recycling and reporting
Compliant recycling of the remains, with the documentation and audit trail your auditors will ask for.
Decommissioning
Tell us what is being retired, and where.
We will handle secure destruction and compliant disposal end to end, with the certificates to prove it.
Sources and notes
- NIST SP 800-88 Rev. 1, Guidelines for Media Sanitization (Clear, Purge, Destroy); IEEE 2883-2022.
- DIN 66399, standardised globally as ISO/IEC 21964: media classes and security levels 1 to 7 with particle-size limits.
- NSA/CSS Evaluated Products List: 6 mm (HDD) and 2 mm (SSD and flash) maximum particle sizes for the highest assurance.
- UK GDPR Article 32 and the Data Protection Act 2018; WEEE Regulations; ADISA ICT Asset Recovery Standard 8.0 (ICO-approved UK GDPR certification); NCSC CAS-S; ISO 27001; NAID AAA.
General guidance, not legal advice. Standards evolve and obligations depend on your data, sector and jurisdiction: confirm current requirements against the relevant standard and, where needed, professional advice. The particle sizes cited are high-assurance benchmarks; the level you need is driven by data sensitivity.