Gas Safety (Installation and Use)

Regulations

3.1 All combustion installations must be accommodated in ways that meet the requirements of the Building Regulations. However, gas installations also have to comply with the Gas Safety (Installation and Use) Regulations, which require anyone undertaking gas work to be competent. Any gas engineering business, whether an employer or self employed, must be a member of a class of persons approved by the Health and Safety Executive (HSE). Because of this, the Building Regulations allow that work need not be notified to Building Control Bodies if it solely comprises the installation of a gas appliance and it is to be undertaken by a member of such an approved class of persons.

The Gas Safety (Installation and Use) Regulations cover the safe installation maintenance and use of gas fittings, appliances and flues. The following paragraphs give builders and lay readers an outline of some of the main requirements of the Gas Safety (Installation and Use) Regulations, but for further information reference should be made to the Health and Safety Commission’s Approved Code of Practice (see below) or Building Control Bodies.

The Gas Safety (Installation and Use)

3.2 Regulations require that (a) gas fittings, appliances and gas storage vessels must be installed only by a person with the required competence and (b) any person having control to any extent of gas work must ensure that the person carrying out that work has the required competence and (c) any gas installation businesses, whether an employer or self-employed, must be a member of a class of persons approved by the HSE; for the time being this means they must be registered with Gas Safe Register.

3.3 Guidance on the individual competency required for gas work is available from the Sector Skills Council Energy and Utility (EU) Skills [http://www.euskills.co.uk/gas]. Persons deemed competent to carry out gas work are those who hold a current certificate of competence in the type of activity to be conducted. Assessment of competence may be through the S/NVQ qualilification under a nationally accredited certification scheme or under the Approved Code of Practice arrangements.

3.4 The Gas Safety (Installation and Use) Regulations control all aspects of the ways combustion systems fired by gas (including natural gas and LPG) are installed, maintained and used, mainly in domestic and commercial premises, and the classes of persons who may undertake gas work. The Regulations may be amended from time to time and whichever
Regulations are currently in force at the time an installation is carried out must be complied with. The advice given below reflects the present state of the Gas Safety (Installation and Use) Regulations following the amendments that came into effect on 31 October 1998.

3.5 The text of the Regulations and guidance on how to comply with them are contained in the Health and Safety Executive (HSE) Approved Code of Practice ‘Safety in the installation and use of gas systems and appliances’. Important elements of the Regulations include that:

a. any appliance installed in a room used or intended to be used as a bath or shower room must be of the room-sealed type;

b. a gas fire, other gas space heater or gas water heater of more than 14kW (gross) heat input (12.7kW (net) heat input) must not be installed in a room used or intended to be used as sleeping accommodation unless the appliance is room sealed;

c. a gas fire, other space heater or gas water
heater of up to 14kW (gross) heat input (12.7kW (net) heat input) must not be installed in a room used or intended to be used as sleeping accommodation unless it is room sealed or equipped with a device designed to shut down the appliance before there is a build-up of a dangerous quantity of the products of combustion in the room concerned;

d. the restrictions in (a)–(c) above also apply in respect of any cupboard or compartment within the rooms concerned, and to any cupboard, compartment or space adjacent to, and with an air vent into, such a room;

e. instantaneous water heaters (installed in any room) must be room sealed or have fitted a safety device to shut down the appliance as in (c) above;

f. precautions must be taken to ensure that all installation pipework, gas fittings, appliances and flues are installed safely. When any gas appliance is installed, checks are required for ensuring compliance with the Regulations, including the effectiveness of the flue, the supply of combustion air, the operating pressure or heat input (or where necessary both), and the operation of the appliance to ensure its safe functioning;

g. any flue must be installed in a safe position and must be adequate, suitable and effective for use with the appliance which it serves;

h. no alteration is allowed to any premises in which a gas fitting or gas storage vessel is fitted which would adversely affect the safety of that fitting or vessel, causing it no longer to comply with the Regulations;

i. LPG storage vessels and LPG-fired appliances

Diagram 31 Types of gas fire

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Gas fires (other than flueless gas fires)

3.6 These appliances fall into the main categories shown in Diagram 31 and the building provisions for accommodating them safely differ for each type.

3.7 Provided it can be shown to be safe, gas fires may be installed in fireplaces which have flues designed to serve solid fuel appliances. Certain types of gas fire may also be installed in fireplaces which have flues designed specifically for gas appliances. The Gas Appliances (Safety) Regulations 1995 require that particular combinations of appliance, flue box (where required) and flue must be selected from those stated in the manufacturer’s instructions as having been shown to be safe by a Notified Body.

Flueless gas appliances

3.8 Flueless appliances should meet the requirements, including requirement J2. A way of achieving this would be to follow the guidance on ventilation provisions for flueless appliances beginning at Paragraph 3.15.

3.9 A flueless instantaneous water heater should not be installed in a room or space having a volume of less than 5 m³.

Air supply to gas fires and other appliances

3.10 A way of meeting the requirements would be to follow the general guidance given in Section 1, beginning at Paragraph 1.2, in conjunction with the guidance below.

Flued Decorative Fuel Effect (DFE) fires

3.11 Any room or space intended to contain a DFE fire should have permanently open air vents as described in (a) or (b) below, unless the installation is in accordance with Paragraph 3.12:

a. for a DFE fire in a fireplace recess with a throat, the air vent equivalent area should be at least 10,000mm² (100cm²)

b. for a DFE fire in a fireplace with no throat, such as a fire under a canopy, the air vent should be sized in accordance with Section 2 of this Approved Document, as if the room were intended to contain a solid fuel fire (see Table 1).

3.12 In dwellings with an air permeability greater than 5.0 m3/hr/m2 (see Appendix F), permanently open air vents may not be necessary for DFE fires with ratings not exceeding 7kW (net) that have a flue gas clearance rate (without spilling) not exceeding 70 m3/hour.

Flued appliances other than decorative fuel effect fires

3.13 These appliances include inset live fuel effect (ILFE) fires, radiant convector fires and boilers, in both room-sealed and open-flued variants.

3.14 A way of meeting the requirement would be to follow the guidance in Diagram 32. An example calculation illustrating the use of this guidance is given in Appendix C.

Air supply to flueless appliances

3.15 For some flueless appliances, it may be necessary to provide permanently open air vents and/or make provision for rapid ventilation as recommended in BS 5440-2:2009 or equivalent, to comply with Part F as well as Part J of the Building Regulations. Some ways of meeting the requirement when installing flueless cookers (including ovens, grills or hotplates), flueless water heaters and flueless space heaters are given in Diagram 33.

3.16 A room containing a gas point intended for use with a flueless appliance (such as a gas point for a cooker or a gas point for a space or water heater, the gas point not being adjacent to a flue) should have the ventilation provision required for the installation of that appliance (calculated on the basis that an appliance with the largest rating consistent with the table to Diagram 33 could be installed there).

Diagram 32 Free areas of permanently open air vents for gas appliance installations (other than decorative fuel effect fires or flueless appliances)

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Diagram 33 Ventilation for flueless gas appliances

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Size of natural draught flues for open-flued appliances

3.17 Where builders wish to provide (or refurbish) flues for gas appliances but do not intend to supply the appliances, a way of showing compliance would be to size flues in accordance with Table 5.

3.18 If an existing flue is to be used it should be checked in accordance with Paragraph 1.36.

3.19 For appliances that are CE marked as compliant with the Gas Appliances (Safety) Regulations, flues should be sized in accordance with the manufacturer’s installation instructions.

3.20 Connecting fluepipes should be the same size in terms of diameter and/or equivalent cross-sectional area as the appliance flue outlet. The chimney flue should have at least the same cross-sectional area as that of the appliance flue outlet.

Table 5 Size of flues for gas-fired appliances

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Height of natural draught flues for open-flued appliances

3.21 Flues should be high enough to ensure sufficient draught to safely clear the products of combustion. The height necessary for this will depend upon the type of appliance, the building height, the type of flue and the number of bends in it, and a careful assessment of local wind patterns. For appliances that are CE marked as compliant with the Gas Appliances (Safety) Regulations, compliance with the manufacturer’s installation instructions will meet the requirements.

3.22 Where an older appliance that is not CE marked is to be installed, a way of showing compliance if it has manufacturer’s installation instructions would be:

a. for decorative fuel effect fires, to follow the guidance in BS 5871-3:2001 2005; or

b. for appliances other than decorative fuel effect fires, to follow the calculation procedures in BS 5440-1:2008.

Outlets from flues

3.23 Outlets from flues should be so situated externally as to allow the dispersal of products of combustion and, if a balanced flue, the intake of air. A way of meeting this requirement would be to locate flue outlets as shown in Diagram 34 and Diagram 35.

Note: The plume of wet flue products from condensing boilers, positioned in accordance with the safety distances set out in Diagram 34, can sometimes be considered a nuisance for neighbouring properties. Whilst this nuisance is not considered to be within the scope of building regulations, such installations could be considered as a ‘Statutory Nuisance’ as set out in the Environmental Protection Act. As such installers may wish to adopt the guidance in Chapter 6 of the Guide to Condensing Boiler
Installation Assessment Procedure for Dwellings

Care may also need to be taken to locate flue outlets away from parts of the building that may be damaged by frequent wetting.

Diagram 34 Location of outlets from flues serving gas appliances

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Table to Diagram 34 Location of outlets from flues serving gas appliances

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Diagram 35 Location of outlets near roof windows from flues serving gas appliances

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3.24 Flue outlets should be protected where flues are at significant risk of blockage. Guidance on meeting this requirement is given below.

3.25 Flues serving natural draught open-flued appliances should be fitted with outlet terminals if the flue diameter is no greater than 170mm. Suitable terminals include those appropriately designated in accordance with BS EN 18561:2003, and conforming to BS EN 13502:2002.

The risk of blockage of flues of more than 170mm diameter should be assessed in the light of local conditions. In areas where nests of squirrels or jackdaws are likely, the fitting of a protective cage designed for solid fuel use and having a mesh size no larger than 25mm (but no smaller than 6mm) may be an acceptable provision if the total free area of its outlet openings is at least twice the cross-sectional area of the flue.

3.26 A flue outlet should be protected with a guard if persons could come into contact with it or if it could be damaged. If a flue outlet is in a vulnerable position, such as where the flue discharges within reach from the ground, or a balcony, veranda or a window, it should be designed to prevent the entry of any matter that could obstruct the flow of flue gases.

Provision of flues

3.27 Satisfactory provision of chimneys and fluepipes for gas appliances may be achieved by:

a. following the guidance on the selection of components and the manner of their installation as given in Paragraphs 3.28 to 3.35 and the references to Section 1; or (if the intended appliance is new and of known type)
or (if the intended appliance is new and of known type):

b. i) using factory-made components that achieve a performance at least equal to that corresponding to the designation given in Table 6 for the intended appliance type when tested to an appropriate
European chimney standard (BS EN); and

ii) installing these components in accordance with the guidance in Paragraphs 3.28 to 3.35 and Section 1, as relevant, and in accordance with the appliance manufacturer’s and component manufacturer’s installation instructions.

Table 6 Minimum performance designations for chimney and fluepipe components for use with new gas appliances

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Connecting fluepipe components

3.28 Satisfactory components for connecting fluepipes include:

a. any of the options in Paragraph 1.32; or

b. sheet metal fluepipes as described in BS EN 1856-2:2004; or

c. fibre cement pipes as described in BS EN 1857:2003+A1:2008; or

d. any other material or component that has been certified as suitable for this purpose.

Masonry chimneys

3.29 Masonry chimneys should be built in accordance with Paragraphs 1.27 and 1.28 in Section 1.

Flueblock chimneys

3.30 Chimneys can be constructed from factory-made flueblock systems primarily designed for solid fuel, as described in Paragraphs 1.29 and 1.30 in Section 1. They can also be constructed from factory-made flueblock systems comprising straight blocks, recess units, lintel blocks, offset blocks, transfer blocks and jointing materials complying with:

a. BS EN 1858-1:2003 for concrete flueblocks of at least class D2; or

b. BS EN 1806:2006 for clay/ceramic flueblocks with a performance class of at least FB4 N2.

3.31 Flueblock chimneys should be installed with sealed joints in accordance with the flueblock manufacturer’s installation instructions. Where bends or offsets are required, these should be formed using matching factory-made components. Flueblocks which are not intended to be bonded into surrounding masonry should be supported and restrained in accordance with the manufacturer’s installation instructions.

Factory-made metal chimneys

3.32 Chimneys for gas appliances may be constructed using systems described in Paragraphs 1.42 to 1.46 in Section 1. Factorymade metal chimneys should be guarded if they could be at risk of damage or the burn hazard they present to people is not immediately apparent.

Location and shielding of flues

3.33 Combustible materials in the building fabric should be protected from the heat dissipation from flues so that they are not at risk of catching fire. A way of meeting the requirement would be to follow the guidance in Table 6.

3.34 Where a fluepipe or chimney penetrates a fire compartment wall or floor, it must not breach the fire separation requirements of Part B. See Approved Document B for more guidance.

3.35 Connecting fluepipes and factory-made chimneys should also be guarded if they could be at risk of damage or if they present a burn hazard to people that is not immediately apparent

Relining of flues in chimneys

3.36 Lining or relining flues may be building work and, in any case, such work should be carried out so that the objectives of requirements J2 to J5 are met (see Paragraphs 1.34 and 1.35). Existing flues being re-used should be checked as described in Paragraph 1.36. For flue liners serving gas appliances, ways of meeting the requirements include the use of:

a. liners as described in Paragraph 1.27;

b. liners as described in Paragraph 2.20;

c. flexible stainless steel liners appropriately designated to BS EN 1856-1:2003 (refer to Table 6);

d. other systems suitable for the purpose.

3.37 Flexible metal flue liners should be installed in one complete length without joints within the chimney. Other than for sealing at the top and the bottom, the space between the chimney and the liner should be left empty unless this is contrary to the manufacturer’s instructions. Double-skin flexible flue liners should be installed in accordance with the manufacturer’s installation instructions. BS 715 liners should be installed in accordance with BS 5440-1:2008.

Table 7 Protecting buildings from hot flues

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Diagram 36 Bases for back boilers (installation using a proprietary back boiler enclosure shown)
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Debris collection space for chimneys

3.38 A debris collection space should be provided at the base of a flue unless it is lined, or constructed of flue blocks, or is a factory-made metal chimney with a flue box. This can be achieved by providing a space having a volume of not less than 12 litres and a depth of at least 250mm below the point where flue gases discharge into the chimney. The space should be readily accessible for clearance of debris, for example by removal of the appliance. For gas fires of the type illustrated in Diagram 31 (a) and (b), there should be at least 50mm clearance between the end of the appliance flue outlet and any surface.

Bases for back boilers

3.39 Provisions for back boilers should adequately protect the fabric of the building from heat. A way of meeting the requirement would be to stand back boilers on hearths intended for solid fuel appliances. Alternatively, unless otherwise stated in the appliance manufacturer’s instructions, a way of meeting the requirements would be to stand back boilers on bases complying with Diagram 36.

Diagram 37 Hearths for decorative fuel effect (DFE) and inset live fuel effect (ILFE) fires: minimum plan dimensions of non-combustible surfaces

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Hearths

3.40 Appliances should be placed on hearths unless:

a. they are to be installed so that every part of any flame or incandescent material will be at least 225mm above the floor; or

b. the manufacturer’s instructions state that a hearth is not required.

3.41 Where hearths are required, guidance on their minimum plan dimensions is given in Diagrams 37 and 38. Hearths should comprise at least a (top) layer of non-combustible, non-friable material not less than 12mm thick. The edges of hearths should be marked to provide a warning to the building occupants and to discourage combustible floor finishes such as carpet from being laid too close to the appliance. A way of achieving this would be to provide a change in level.

Shielding of appliances

3.42 Gas-fired appliances should be located where accidental contact is unlikely and surrounded by a non-combustible surface which provides adequate separation from combustible materials. For appliances that are CE marked as compliant with the Gas Appliances (Safety) Regulations, a way of meeting the requirement would be to adopt the manufacturer’s instructions. An alternative approach would be to protect combustible fabric with:

a. a shield of non-combustible material, such as insulating board, with a fire-resistant surface; or

b. an air space of at least 75mm (see Diagram 39).

Diagram 38 Hearths for other appliances: plan dimension of non-combustible surfaces

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Diagram 39 Shielding of appliances

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Alternative approach

The requirements may also be met by adopting the relevant recommendations in the publications listed below to achieve an equivalent level of performance to that obtained by following the guidance in this Approved Document:

BS 5440 Installation and maintenance of flues and ventilation for gas appliances of rated input not exceeding 70kW net (1st, 2nd and 3rd family gases), Part 1:2008 Specification for installation and maintenance of flues; Part 2:2009 Specification for installation and maintenance of ventilation for gas appliances. BS 5546:2000 Specification for installation of hot water supplies for domestic purposes, using gas-fired appliances of rated input not exceeding 70kW.

BS 5864:2004 Specification for installation in domestic premises of gas-fired ducted-air heaters of rated input not exceeding 60kW.

BS 5871 Specification for installation of gas fires, convector heaters, fire/back boilers and decorative fuel effect gas appliances, Part 1:2005 Gas fires, convector heaters and fire/back boilers and heating stoves (1st, 2nd and 3rd family gases); Part 2:2005 Inset live fuel effect gas fires of heat input not exceeding 15kW and fire/back boilers (2nd and 3rd family gases); Part 3:2005 Decorative fuel effect gas appliances of heat input not exceeding 20kW (2nd and 3rd family gases). BS 6172:2004 Specification for installation of domestic gas cooking appliances (1st, 2nd and 3rd family gases).

BS 6173:2001 Specification for installation of gas-fired catering appliances for use in all types of catering establishments (2nd and 3rd family gases).

BS 6798:2009 Specification for installation of gas-fired boilers of rated input not exceeding 70kW net.

Section 3: Additional provisions, for gas burning appliances