Thanks for the quick replies.
The room is a small brick outhouse, probably 5-6 cubic meters with a door and opening window, it was probably the gardeners shed in an earlier life. The fire tray and grill are in the order of 1m x 0.5m and are at work top level. There is a sheet metal pyramid canopy about 600 mm above the grill covering the whole of the grill area; this reduces to a round 210mm dia. hole. The inlet of an inline fan should locate on top of the canopy in the 210mm hole. The exhaust is forced up a 1m vertical 210mm dia. chimney fitted to the fan outlet, with a conical rain guard on top, there is a good gap between the top of the chimney and the rain guard. The canopy is as low as is comfortable for the user so I can’t move it down closer to the source, which leaves a maximum gap between the top of the canopy and the sloping roof that will accommodate a cube of about 250 mm. I have looked at roof mounted fans but the shape of the roof makes that a difficult if not impossible option. Originally a Systemair axial fan was used but cut out if the temp. went over 150 deg C, this link goes to the fan used
http://catalogue.systemair.com/COM/index.aspxThe second attempt is fine with the high temp but does not remove anything like enough smoke, there is a pdf. manual at
http://www.ecoangus.co.uk/ecoangus_imag ... manual.pdf. This fan unit just fits in the space available.
Sorry about the wordy description, it never occurred to me to take photographs and my colleague, and the BBQ live on the other side of the city.