<p>Roof drying apparatus (10) comprises : a housing (12) having one or more air inlets (26) and an air outlet (40); an internal combustion engine (24) mounted in the housing (12); and a blower mechanism (34) which is drivable by the engine (24) for forcing air out of the air outlet (40) of the housing (12). The apparatus is characterised in that an exhaust outlet (30) of the engine (24) is positioned to discharge exhaust gas in or onto an air flow path which extends from the or at least one of the air inlets (26) to the air outlet (40) so that, in use, at least a portion of the air outputted from the air outlet (40) by the blower mechanism (34) is pre-heated by the exhaust gas of the engine (24). A duct device for adapting an internal combustion engine handheld air blower device to form such roof drying apparatus is also provided.</p>
