Objective of this thesis is to show that unprotected steel in case of localized fire regarding single large span, tubular trussed industrial hall frame (supermarket hall) may satisfy fire resistance that is required by Swedish code [6] for this kind of structures (R30).There are two main sources of resistance increase that shall be taken into account:Restraining effect of steel sheeting (roofing)Usage of more realistic temperature development modelRegarding first source of resistance increase (roof effect), it shall be proven that hand calculation method that exists in EN 1993-1-2 [4] applied to this kind of structures yield more conservative results as the roof effect isn’t taken into account.Second source of resistance increase comes from assumption that in volumetrically large spaces (supermarkets etc.) flashover effect can’t occur. Gas layer that accumulates under the ceiling due to large volume of the enclosure is not sufficient to induce flashover effect. For the purpose of comparison and investigation of effect of fasteners, ISO 834 nominal fire curve shall be used.