Office fire safety: bringing buildings up to code and turnkey works
Exit units: sizing escape routes according to the French Labour Code
A category A fire safety system (SSI) on a 300 m² floor plate under a short lease means 15,000 EUR in extra cost for zero regulatory gain: article R4227-5 of the French Labour Code and standard NF S 61-931 allow a category E SSI with a type 4 alarm. Fire safety in office buildings rests on four pillars: fire compartmentation rated 1 h (EI 60), smoke extraction for circulations longer than 30 m, category A to E SSI, and escape routes measured in exit units. Since 2006, Kytom has supported bringing premises up to standard on occupied sites, with an average lead time of 12 weeks, validation by an approved inspection body and phasing by zones of 150 m² to 250 m². As an Office Manager, Property Director or CFO, you often inherit the file without having chosen its timing: a commission visit, an observation from a technical inspector, a new lease or a refit trigger the urgency. This page details the technical ratios, the regulatory checkpoints (Q18 and Q19 CNPP standards, NF S 61-933) and the method to carry out the works without interrupting operations.
Escape routes govern evacuation and rely on the concept of the exit unit (UP) defined in article R4227-5 of the French Labour Code. One UP corresponds to a width of 0.60 m to 0.90 m, two UP require 1.20 m to 1.40 m, three UP require a minimum of 1.80 m.
The number of UP required depends on the theoretical occupancy of the floor plate:
- up to 19 people: 1 UP, 1 exit
- from 20 to 50 people: 2 UP, 2 separate exits
- from 51 to 100 people: 2 UP, 2 exits
- above 100 people: 1 additional UP per 100-person band
Articles R4227-4 to R4227-9 require at least two opposite exits from 50 people or 300 m². A 0.90 m door counts as 1 UP, a 1.40 m door as 2 UP. A single staircase 1.40 m to 1.50 m wide allows a maximum occupancy of 100 people per floor according to article R4227-5.
For the CFO: theoretical occupancy drives CAPEX, not actual occupancy. The authorities use the theoretical occupancy calculated on the usable floor area (1 person per 10 m² in a standard office), not the number of active badges. On an 800 m² floor plate occupied by 50 actual people but theoretically sized for 80, you need two 2-UP exits, meaning two 1.40 m doors and two compliant stairwells. Anticipating this calculation as soon as the lease is signed avoids 25,000 EUR to 60,000 EUR of structural rework.
Kytom checks these ratios from the concept stage, before the partitioning plans are finalised. An approved inspection body validates compliance before handover.
Contrarian view: industry conventional wisdom over-applies UP to small floor plates. On a floor plate of fewer than 19 people with a single, already compliant exit and no planned change in occupancy, triggering a full UP study is disproportionate: a visual audit by a technical inspector is enough. For a firm lease of less than 24 months, resizing exits for a theoretical occupancy not reached in practice generates a cost with no realistic amortisation: it is better to submit a reasoned exemption request to the safety commission, which is generally received favourably when the file is solidly argued.
Frequently asked questions
Which SSI category for a 500 m² office floor plate?
Below 500 m² with no high-risk room, a category E SSI with a type 4 alarm is sufficient according to NF S 61-931. Above that, or with a server/archive room, a category A SSI becomes relevant. Systematic validation by an approved inspection body before finalisation.
