The unit for the section factor is m
-1. The thinner the profile, the higher the section factor and more quickly the profile is heated. To clarify: for higher section factors, a higher thickness of fire protection is required whereas for lower section factors less protection is required, on condition that beams with the same critical temperature are compared.
To summarize, to determine the thickness of any system for the fire protection of steel structures, critical temperature and section factor both have decisive roles. The manufacturers of protection have the tables for each of their products which, for a particular level of fire protection, indicate thickness depending on the critical temperature and section factor. However, it is necessary to pay attention that the system is tested in accordance with EN 13381 and classified in accordance with EN 13501, as there are still products available on the market which do not correspond to criteria and represent, due to their easier testing conditions, unfair competition and danger in the case of a real fire.