An EI120 classification looks simple on paper. Two systems achieve the same fire resistance rating. Both are tested. Both are documented. Both may even be CE-marked and supported by European assessment frameworks. From a procurement perspective, they can quickly appear interchangeable. In practice, they rarely are.
One of the most common misconceptions in passive fire protection is the assumption that equivalent EI classifications represent equivalent system performance. The industry often reduces highly complex firestop assemblies to a single number and overlooks the engineering conditions that made those classifications possible.
The Problem with Comparing Systems by Rating Alone
Construction projects naturally favour simplification. A specification may require EI120 firestopping, and by the time the requirement reaches procurement, the conversation often becomes focused on cost, availability, and installation speed.
The problem is that fire resistance classifications are not standardised product performance metrics. Two systems may achieve the same EI120 rating through entirely different tested configurations. The classification matches. The underlying assumptions do not.
The same EI rating does not mean the same tested configuration, application scope, or installation tolerance.
The Building Is Not a Laboratory
Fire testing takes place under controlled conditions. Buildings do not. Services move during installation. Openings become irregular. Penetrations are modified by multiple trades. Access becomes restricted. Design changes occur long after the original firestop solution has been selected.
Under these conditions, system resilience becomes just as important as classification. Some systems tolerate variation relatively well, while others are highly sensitive to seemingly minor deviations from the tested arrangement.
The closer an installation remains to the tested configuration, the more meaningful the EI classification becomes.
Flexibility Does Not Always Mean Robustness
Another misconception is that broader application scope automatically means better performance. Some firestop systems are designed to accommodate a wide variety of services and penetration arrangements, which can be valuable on complex projects.
However, highly flexible systems can also become more dependent on installation quality, sequencing, and coordination. Meanwhile, systems with narrower application limits may sometimes deliver more predictable results on site.
- Different installation tolerances
- Different inspection requirements
- Different workmanship dependencies
- Different sensitivities to site variation
Why ETA Scope Matters
A shared classification does not mean a shared approval scope. An EI120 system may have strict limitations relating to substrates, opening dimensions, service combinations, or insulation arrangements. Another EI120 system may have significantly broader assessed application boundaries under its ETA.
As projects evolve, penetrations frequently change from simple openings into mixed-service arrangements. When that happens, a system that once appeared suitable may no longer fit within its assessed scope, even though the required fire rating remains unchanged.
Compare the installed condition against the ETA scope, not only against the required EI rating.
The Industry Is Moving Beyond Rating-Based Thinking
Modern construction projects are becoming increasingly documentation-driven. Across Denmark and the wider European market, expectations around traceability, digital documentation, verification, and system identification continue to grow.
An EI classification remains essential. It provides a common language for fire performance. But it is only the visible outcome of a much larger engineering story.
As buildings become more complex, the most important question is no longer whether two systems share the same rating. It is whether they share the same level of confidence once they leave the laboratory and become part of a real building.