Structural failure of such beams, whether created within a rolled section or during fabrication, may be very different than normal beams and it is for the designer to provide the limiting temperature for any section design, taking account of the nature of the critical stresses.
Guidance on the appropriate product performance testing and the procedure for determining the appropriate thickness of any product designed to provide the required fire protection to these types of beam, is detailed in the ASFP (Association for Specialist Fire Protection) publication Fire Protection For Structural Steel In Buildings (well known as the ‘Yellow Book’). In the case of intumescent coatings, however, the current guidance is limited to beams with circular openings, claims the Association. Some steel beam manufacturers already have proprietary software that can reliably provide the necessary information for beams with other shaped openings. Without such data, manufacturers of intumescent coatings cannot specify the required product thickness for beams with non-circular openings. 
The current position is as follows. Firstly, beams with circular openings may be protected by any intumescent product that has undertaken the ASFP protocol for beams containing circular openings. Secondly, beams with elongated circular openings may be protected as with circular openings, provided a ‘limiting temperature’ is available from the beam fabricator or the Structural Engineer for the project. Thirdly, with regard to beams with openings other than the above, the ASFP and the SCI have recently agreed to develop a protocol for evaluating the performance of intumescent coatings used to fire protect beams with rectangular and other shaped web openings.
The protocol, which would allow manufacturers to conduct the necessary test and assessment work could, however, take at least a year to complete. In the meantime it is recommended that, unless the appropriate critical design data is available for a specific beam design, product performance data obtained from the ‘ASFP Yellow Book’ testing and assessment protocol for beams containing circular openings, may be used as a basis of providing fire protection to beams with non-circular openings; assuming that the critical design temperature of the steel beam does not exceed 450C. It will be up to the designer to decide whether this limiting temperature is adequate for all modes of structural failure at the fire limit state.
