1.1 This Standard has been drafted by a Panel appointed by the Institution of Gas Engineers and Managers’ (IGEM’s) Gas Utilization Committee and is published by the authority of IGEM’s Council. 
 
1.2 This Standard summarises best practice in the use and maintenance of new and existing “shared flues” systems i.e. shunt duct, Se-duct, U-duct systems, and fabricated shared chimney/flue systems (communal flue systems (CFSs)). 
 
The intention is to make designers, installers, maintenance persons and landlords aware of the safety issues surrounding the use of shared flue systems.  
 
1.3 This Standard makes use of the terms “must”, “shall” “should” and when prescribing particular requirements. Notwithstanding Sub-Section 1.6: 

• the term “must” identifies a requirement by law in Great Britain (GB) at the time of publication 
• the term “shall” prescribes a requirement which, it is intended, will be complied with in full and without deviation 
• the term “should” prescribes a requirement which, it is intended, will be complied with unless, after prior consideration, deviation is considered to be acceptable. 

 
1.4    It is now widely accepted that the majority of accidents in industry generally are in some measure attributable to human as well as technical factors in the sense that actions by people initiated or contributed to the accidents, or people might have acted in a more appropriate manner to avert them. 
 
It is therefore necessary to give proper consideration to the management of these human factors and the control of risk. To assist in this, it is recommended that due regard be paid to HSG48. 
 
1.5    The primary responsibility for compliance with legal duties rests with the employer. The fact that certain employees, for example “responsible engineers”, are allowed to exercise their professional judgement does not allow employers to abrogate their primary responsibilities. Employers must: 

• have done everything to ensure, as far as is reasonably practicable, that there are no better protective measures that can be taken other than relying on the exercise of professional judgement 
• have systems and procedures in place to ensure that the exercise of professional judgement by “responsible engineers” is subject to appropriate monitoring and review 
• not require “responsible engineers” to undertake tasks which would necessitate the exercise of professional judgement that is beyond their competence. There should be written procedures defining the extent to which “responsible engineers” can exercise their judgement. When “responsible engineers” are asked to undertake tasks which deviate from this, they should refer the matter for higher review. 

 
1.6    Notwithstanding Sub-Section 1.3, this Standard does not attempt to make the use of any method or specification obligatory against the judgement of the responsible engineer. Where new and better techniques are developed and proved, they should be adopted without waiting for modification of this Standard. Amendments to this Standard will be issued when necessary and their publication will be announced in the Journal of IGEM and other publications as appropriate. 
 
1.7    Requests for interpretation of this Standard in relation to matters within its scope, but not precisely covered by the current text, should be addressed to Technical Services, IGEM, IGEM House, High Street, Kegworth, Derbyshire, DE74 2DA and will be submitted to the relevant Committee for consideration and advice, but in the context that the final responsibility is that of the engineer concerned. If any advice is given by, or on behalf of, IGEM, this does not relieve the responsible engineer of any of his or her obligations. 
 
1.8    This Standard was published in July 2011. 
 
  

2.1     This Standard covers the use, maintenance and de-commissioning of shared flue systems comprising: 

• shunt ducts 
• Se-ducts 
• U-ducts
• fabricated shared chimney/flue systems (communal flue systems) (CFSs). 

installed in buildings containing multiple individual dwellings. This includes the installation of replacement appliances onto existing systems. 
 
Note 1: The principles of the Standard may equally be applied where such a flue design is used in a building containing a single dwelling or in single or multiple commercial or industrial units. 
 
Note 2: It is important to differentiate between traditional shared flue systems i.e. shunt ducts, Se-ducts and U-ducts, and the more modern CFSs. 
 
Note 3: It is assumed that any CFS is of a proprietary design and of materials that are fit for purpose. 
 
This Standard does not address the installation of new shared flue systems. Once such systems are in place, this Standard applies to their subsequent use, maintenance and de-commissioning, and to the replacement of appliances. 
 
 Note:     Advice on the installation of new shared flue systems is given in BS 5440-1. 
 
2.2 This Standard applies to shared flue systems that serve domestic appliances burning any gaseous fuel. 
 
2.3 This Standard assumes replacement domestic appliances installed onto a shared flue system are CE marked and are suitable for the system to which they are intended to be installed. 
 
2.4  Italicized text is informative and does not represent formal requirements. 
 
2.5 Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections via the prescriptive terms “must”, “shall” or “should”.