HSE publishes guidance (in the form of leaflets, books and on its webpages) and Approved Codes of Practice (ACOPs).
HSE guidance provides advice to help you understand how to comply with the law; explanations of specific requirements in law; specific technical information or references to further sources of information to help you comply with your legal duties.
ACOPs describe preferred or recommended methods that can be used (or standards to be met) to comply with regulations and the duties imposed by the Health and Safety at Work etc Act.
The legal status of guidance and ACOPs is given below and will appear in the relevant publications.
HSE guidance legal status
This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory, unless specifically stated, and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance.
Approved Codes of Practice (ACOPs) legal status
Each ACOP is approved by the Health and Safety Executive, with the consent of the Secretary of State. It gives practical advice on how to comply with the law. If you follow the advice you will be doing enough to comply with the law in respect of those specific matters on which the Code gives advice. You may use alternative methods to those set out in the Code in order to comply with the law.
However, the Code has a special legal status. If you are prosecuted for breach of health and safety law, and it is proved that you did not follow the relevant provisions of the Code, you will need to show that you have complied with the law in some other way or a Court will find you at fault.
The above is extracted from http://www.hse.gov.uk/legislation/legal-status.htm
If you need help implementing the guidelines in ACoP L8 and HSG 274 concerning managing Legionella then contact Collaton Consultancy Limited on firstname.lastname@example.org or phone on +44 (0)7958 124563