The ASFP Yellow Book changes to Critical Temperature and what this means for you?

The Yellow Book changes to Critical Temperature and what this means for you?

TheAssociation for Specialist Fire Protection (ASFP) has revised its guidelines on critical temperatures selection. Tremco CPG and Nullifire are active members of the ASFP and are heavily involved in developing and driving standards for the fire protection industry. 

ASFP’s Yellow Book gives guidance on many aspects of structural steel protection with one key area being the default critical temperature (or limiting temperature) that should be used if the structural loading conditions are unknown preventing precise calculation.

The ASFP have recently just published its latest revision which simplifies the default temperatures. 

The critical temperature is the maximum that structural steel should be allowed to reach in each duration to prevent collapse. 

 Yellow Book has gone through several revisions with Revision 5 issued in July 2014. Over recent years, there has been a greater involvement and understanding of structural engineering in the industry, and particularly structural fire engineering. This has led to questions being raised over whether the default critical temperatures are sufficiently conservative. This has been the focus on the latest Rev 6, which has been in draft form for a significant time. After reaching agreement towards the end of 2024, Yellow Book Revision 6 (volume 1 only) was published in January 2025.

There are significant differences in the advice given between Rev 5 and Rev 6. Rev 5 had several tables for different design codes and occupancies that were difficult to understand and interpret. Rev 6 takes a much more simplified approach with a single table. 

Given that there are concerns over how widely Rev 5 is understood and the changes with Rev 6, Tremco CPG find it important to clarify the situation. 

This is because different critical temperatures can have a significant impact on the amount of fire protection needed. A project that is being bid on by different suppliers may appear to have significantly different competitive positions if the same critical temperatures are not being used. It may appear that the customer may have to apply more coating to achieve the same level of protection if a lower critical temperature is used.

In summary, the changes that have been made as guidance to the market are:

Tremco CPG remains at the disposal of our customers to support and advise where necessary. 

If there are any issues regarding these new guidelines, reach out and contact a member of our technical team who will assist with any enquiries.