Specifies the requirements and test methods for the construction, safety, classification and marking of non-domestic gas-fired overhead radiant tube systems incorporating two or more burner units with each burner under the control of an automatic burner control system, and operated by a single fan providing a single flue outlet, called system H and referred to in the body of the text as the "system". Applicable to Type B[22] systems intended for use in other than domestic dwellings, in which the supply of combustion air and the evacuation of the products of combustion is achieved by mechanical means. Applicable only to such systems that have fully pre-mixed gas/air burners. Applicable to systems which are intended to be type tested.