Standards
The difference between E, EW and EI: classifications explained
E, EW and EI are the European classifications for the fire resistance of separating constructions according to EN 13501-2. The letters indicate what the construction holds back: E stands for integrity (flame-tightness), W for reduced heat radiation and I for thermal insulation. The number that follows is the time in minutes that this performance is maintained in the fire test, for example EW 60. Below you can read what each criterion means and when to specify which requirement.
What does E (integrity) mean?
A construction with class E holds back flames and hot combustion gases for the classified time. However, there are no limits on the temperature on the non-fire side or on the heat radiation passing through the construction. Class E is therefore the basic performance: suitable where fire breakthrough must be prevented, but where no people need to escape close along the separation and no combustible materials stand directly behind it.
What does EW (reduced heat radiation) add?
Class EW adds a limit on heat radiation to the flame-tightness: measured at one metre from the construction, it may not exceed 15 kW/m². As a result, the space behind the curtain remains usable for longer and materials at some distance do not ignite. In practice EW is the most commonly specified requirement for fire curtains, for example when an escape route runs a few metres from the separation.
When is EI (thermal insulation) required?
Class EI adds requirements on the temperature of the non-fire side to the flame-tightness: on average no more than 140 °C and locally no more than 180 °C above the initial temperature. The separation then holds back the heat almost completely. EI is required where people or combustible materials may directly adjoin the separation, such as at extra protected escape routes and between fire compartments with occupied functions. For flexible fabric curtains EI is technically the most demanding class.
Which classification does your project need?
The Dutch Building Decree (Bbl) or the fire safety consultant determines the requirement per separation; the classification in the curtain's test report must at least match it, including the duration. If you are unsure between EW and EI, look at what happens directly behind the separation: if people escape right alongside it or storage adjoins it, EI is the obvious choice. You will find a comparison of fire and smoke curtains on our fire safety page.
More background on standards and classifications? Read the fire safety information.
Further reading
Regulations
When is a smoke curtain mandatory?
Dutch building regulations set requirements for smoke spread. In these situations a smoke curtain is the appropriate solution.
Practice
Fire compartmentation in atriums: how to approach it
An atrium by definition breaks through the compartmentation. Flexible curtains solve this without losing the openness of the design.