On the ground, the calculation of passage units rarely presents itself as a theoretical exercise. It is most often discovered when an inspector points out a door that is too narrow, or when a compliance file returns with observations. The width of a corridor, the size of an emergency exit, the number of available exits: everything hinges on this notion of UP, and an error in sizing can block the operation of a public establishment.
Field Verification of UP: What Gets Stuck During ERP Inspections
When a control organization (SOCOTEC, Bureau Veritas, APAVE) visits an establishment, the verification of exits is part of the systematic checks. It is not just about whether the doors exist; we measure their actual usable width, with the leaves open.
The most common trap concerns double-leaf doors where only one leaf is kept open during regular operation. The passage width considered by the inspector is that of the main leaf only, unless an automatic unlocking device releases the second leaf in case of an alarm. Without this device, only the active leaf counts in the calculation of UP.
We also regularly encounter issues with staircases: a guardrail or handrail that encroaches on the usable width reduces the number of available UP. A few centimeters are enough to fall below the regulatory threshold. To properly understand how to calculate UP in ERP, one must start from the actual measurement between walls or between handrails, not from the dimension on the plan.
Actual Width of a Passage Unit: The Thresholds That Change Everything
The base width of a UP is set at 0.60 meters. At first glance, this seems simple. In practice, two derogatory thresholds modify this value and generate the majority of sizing errors.
- For a single UP, the minimum required passage width is 0.90 meters, not 0.60. This threshold applies to small establishments with a limited number of people.
- For two UP, the minimum width increases to 1.40 meters in total, not 1.20 (2 x 0.60). This upgrade aims to ensure the crossing of two flows of people.
- Beyond two UP, we return to linear calculation: each additional UP adds 0.60 meters. Therefore, three UP require 1.40 + 0.60 = 2.00 meters.
These specific thresholds for one and two UP are the most common source of error in files. We regularly see plans dimensioned at 1.20 meters for two UP, which is insufficient.
Link Between Capacity and Required Number of UP
The number of UP needed directly depends on the maximum capacity allowed in the establishment. The general rule for ERP of the first four categories provides for an exit for the initial public tranche, then additional exits for each tranche of capacity.
For 5th category ERP (the smallest), the obligations are relaxed but not nonexistent. Recent regulatory developments are actually strengthening fire safety requirements for this category, with a direct impact on evacuation plans.
Articulating UP, Exits, and ERP Category in the Same Calculation
Competitors often treat the calculation of UP in isolation. In practice, the difficulty arises from the articulation between three simultaneous parameters: the number of exits (how many exits), the number of UP per exit (what width for each exit), and the category of the establishment (which rules apply).
Let’s take a concrete case. A restaurant with a public capacity exceeding the threshold of the 5th category must have at least two distinct exits. Each of these exits must offer a number of UP proportional to the capacity it serves. The calculation is done exit by exit, not for the entire building.
The distinction between normal exits and emergency exits also matters. A normal exit is included in the basic regulatory calculation. An emergency exit can complement the system but does not replace a missing normal exit. One does not compensate for a main door that is too narrow with an additional emergency exit.
Case of Horizontal Circulations and Staircases
Corridors and horizontal circulations must also comply with UP sizing. A corridor serving multiple rooms must be sized for the cumulative capacity of all the rooms it serves, not just for the largest room.
For staircases, the width is measured between handrails, not between walls. This precision frequently changes the result. A staircase measured at 1.40 between walls may drop to 1.20 between handrails, which is no longer sufficient for two UP.
Bringing UP into Compliance After Inspection: Steps to Follow
When an inspection report identifies a non-compliance regarding exits, correction rarely involves major work. In most cases, three levers are used.
The first is the revision of the declared capacity. If the operator can justify a real capacity lower than that initially declared, the number of UP required decreases. This requires reviewing the declaration with the safety commission with factual elements (layout plans, number of fixed seating places).
The second lever concerns the replacement or modification of door frames. Sometimes, widening a passage by a few centimeters is enough to gain an UP. The third concerns handrails and guardrails, whose repositioning can free up the necessary usable width.
Feedback varies on this point depending on local safety commissions, but the logic remains constant: compliance is demonstrated through physical measurement, not by the architect’s plan. On the day of the commission meeting, it is the tape measure that decides.