What is BS 5258-9- Safety specification for combined gas appliances about? 
BS 5258 is a British Standard that discusses safety of domestic gas appliances. The aim of the BS 5258 series is to provide specific requirements for safe use of combined gas appliances.
BS 5258-9 is the ninth part of the series that specifies safety requirements and describes associated methods of test for gas-fired combined appliances consisting of a fanned-circulation ducted-air heater together with a circulator.
BS 5258-9 also covers fanned-circulation ducted-air heaters which are designed to be fitted with circulators, as a purchaser’s option.
BS 5258-9 only applies to circulators intended for use as an integral part of the combined appliance. Circulators intended for independent use are covered by BS 5258-1.
BS 5258-9 covers appliances in which the rated heat input of the air heater does not exceed 60 kW and that of the circulator does not exceed 8 kW.
Note 1: BS 5258-9 is not applicable to:
- Flueless appliances
- Type C appliances burning 3rd family gas
- Appliances incorporating full sequence automatic control systems
- Appliances with premixed gas and air burners
- Appliances designed to make use of the latent heat of condensation of the water vapour in the combustion products.
Note 2: BS 5258-9 does not include the special requirements for appliances for outdoor installation or for appliances with fan-powered combustion circuits or fan-assisted flues.
Who is BS 5258-9 - Safety specification for combined gas appliances for? 
BS 5258-9 on safety specification for combined gas appliances is relevant to: 
- Manufacturers of gas appliances
- Product designers
- Ductwork installers
- Quality control and testing personnel
Why should you use BS 5258-9- Safety specification for combined gas appliances?
Combined appliances for the ventilation system carry gas through them. Improper construction and poor maintenance of it can lead to fire hazards and leakages in duct systems associated with these combined appliances. Hence, these appliances need to be tested for their most efficient functioning.
BS 5258-9 walks you through the test conditions and general requirements, enabling you to test for gases such as TGA, NGA, LPGA, and LPGC with corresponding inlet pressures to ensure the prevention of leakage and reduction of risks in gas appliances.
BS 5258-9 provides you guidance on general design and construction, including materials, fittings, finishes, component location, materials in contact with gas, bolts, screws, insulation and more, enabling you to ensure the operational safety and stability of the systems.
In order to minimize the risks of hazards, BS 5258-9 also discusses the installation and servicing procedure for safe use of the product over time.
With obedience and compliance to BS 5258-9, you can develop and assess combined gas appliances to ensure safety and prevention of hazards over their operational life.
