Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 133,119 pages of information and 210,773 images on early companies, their products and the people who designed and built them.
of Selas Works, City Road, Manchester. Telephone: Central 2648. Telegraphic Address: "Selasgas, Manchester"
Presumably the British subsidiary of SELAS Heat Technology of USA
1925 Patent x 2 - Improvements relating to apparatus for controlling the proportions of gases in mixtures.
1937 British Industries Fair: Advert as part of the Incandescent Furnace Group. Designers and Manufacturers of Industrial Gas Equipment for all Purposes in all Trades. Apparatus, Plant, Equipment, Furnaces, Ovens, Burners. Specialities and accessories for every industrial heating process and purpose, and with use for all fuels. (Engineering/Metals/Quarry, Roads and Mining/Transport Section - Stand Nos. D.327 and D.226) 
1937 Industrial heating equipment manufacturers. "Selas" Heating Equipment.