Electromagnetic advice for computer builders

This advice is designed to provide basic guidance to traders. It is not a complete or authoritative statement of the law. Please note that some of the advice we provide to businesses is chargeable.

If you build, refurbish or upgrade computers then you need to comply with the law on electrical interference and electromagnetic compatibility before you can legally sell them. This advice is designed to help you comply.


Do the Regulations apply to me if I only put the components together?

Yes, the law regards you as a manufacturer if you put together the various components that make up a computer, such as a case with power supply unit, a motherboard and processor, hard drives, CD ROM etc.

This applies even if all the components are individually CE marked by their manufacturer.

However, the other components that would make up a 'complete computer system' such as the monitor, keyboard and mouse, provided they are CE marked by their manufacturer, are not usually regarded as your responsibility.

What are the requirements?
  • Your products must not interfere with, or be prone to interference from other electrical or electronic goods (EM pollution)
  • You must issue a Declaration of Conformity and keep it for 10 years
  • The final product must be CE marked by you to show it complies

As the manufacturer, you are deemed to be responsible for ensuring the final product meets the requirements of the law.

Failure to comply with any of the requirements could lead to a criminal prosecution of the company and its directors, with a maximum fine of £5,000 and/or 3 months in prison, for each offence. Steps can also be taken to remove non-compliant products from the market and have them destroyed

How can I do that?

There is no straightforward answer to this.

The nature of EM pollution means the only certain way to show your products do not produce EM pollution is to have each product individually tested against the relevant product standards.

It is recognised that this not practical or reasonable, in most cases. By adopting a risk assessment strategy, the burdens can be significantly reduced.

The DTI gives the following advice:

"When self certifying, the manufacturer takes responsibility for his products' performance. He must be confident that his products meet the essential requirements of the EMC Directive and is responsible for deciding what measures are necessary to achieve this. If he decides to conduct minimal tests, or none at all, he must assess the risk of so doing and be prepared to justify his action to the enforcement authority in demonstrating compliance, if so requested".

As the enforcement authority we offer the following advice:

  • doing nothing and/or pleading ignorance is never the right thing to do
  • build an example that contains all the latest and fastest components and have it pre-compliance tested by a recognised testing laboratory. In this 'worst case' scenario, if the results show it passes, then any lesser systems should also pass
  • using only CE marked components does not mean the final result will meet the requirements. However, by using only CE marked components, a good quality case and adopting good engineering practice during the construction can help to ensure the final produce is more likely to pass
  • keep a Technical File which shows the source of your components and that they are CE marked
  • in addition to the EM pollution requirements, the regulations also require that a manufacture produces and signs a Declaration of Conformity for each type of system he supplies
Self certifying

If using the self certifying or standards route to compliance, this document must :

  • be written in English
  • give the name and address of the responsible person or, where the responsible person is not the manufacturer, the manufacturer's name and address
  • be signed by or, on behalf of, the manufacturer and identify the signatory
  • bear the date of issue
  • include a description of the apparatus to which it refers, ie all the component parts used, motherboard, processor, HDD, FDD, etc
  • give the number and title of the Harmonised standards used
  • certify that the apparatus to which it relates conforms with the protection requirements of Council Directive 89/336/EEC

A single Declaration of Conformity can describe a number of models or variations. This could be used where the components are likely to vary but the overall EM characteristics of the system stay the same or lower, as in the worst case scenario.

You must be able to produce a copy of this Declaration of Conformity when asked to by the Enforcement Authorities.

You must also keep the Declarations of Conformity available for inspection for 10 years after the last example was supplied.