Partitions shall fulfil one or more of the following criteria for avoiding fire propagation:
- E: Integrity & Stability – ability to stop flames and hot gases from penetrating.
- I: Insulation – ability to restrict the temperature rise on the cold side. In most cases, the temperature at the cold surface may not increase more than 140 degrees Celsius on average, or 180 degrees locally, compared to the initial temperature.
- R: Loadbearing function – ability of a structure to carry loads or actions without collapsing. Only applicable to partitions if the fire compartmentation boundary has also loadbearing functions.
The fire resistance is always expressed in time, usually in classes that are multiples of 30 minutes. For example, a loadbearing compartment floors, that can withstand fire during at least 120 minutes will be “REI120”, and a sandwich (no-loadbearing) partition wall that keeps the flames out and temperatures low during at least 120 minutes will be “EI120”.
The E and I criteria are intended to stop fire propagation. In case of only an “E” (integrity & stability) requirement, the temperature of the unexposed surface can increase without restrictions. But if the unexposed surface reaches high temperatures, the combustible materials in the adjacent (non-fire) compartment may spontaneously ignite. This would cause the fire to spread to this compartment even before flames or hot gases penetrate the partition. To avoid this, also the “I” (insulation) requirement is required for fire compartment, escape routes , floors, etc.
In an element classified “EI” or, if loadbearing, “REI”, cold smoke may penetrate through the partition, as only hot gases are considered by the test standards. During a fire, the heat will activate for example intumescent materials in joints and penetration seals and create a tight boundary. But in the stage before the fire reaches the partition, the cold smoke may penetrate through the partition. This will normally not cause fire propagation, but smoke is often harmful to the occupants of a building. Avoiding smoke propagation is done best with products that are tightly fitting together without leaving gaps, preferably combined with a smoke extraction system to provide a way out for the smoke without building up overpressures. (for example PROMASEAL® Sealants)