The fatal incident at the OXY building renovation site in central Brussels on July 14, 2026, exposes a critical vulnerability in urban construction: the physical transformation of vertical transit shafts into high-velocity thermal ducts. When a fire erupted on the second floor of the former administrative headquarters at Place de Brouckère, the rapid escalation did not occur across horizontal floor plates. Instead, the failure vector was entirely vertical. Flames penetrated the open lift shafts, bypassing initial containment efforts and triggering a secondary fire in the second basement level.
This disaster highlights a structural blind spot in safety protocols during the active refurbishment phase of high-rise assets. Understanding why these environments fail catastrophically requires analyzing the physical forces of thermal updrafts, the stark differences between active construction zones and finished buildings, and the mechanical failure rate of hoist systems.
The Thermodynamics of the Unfinished Shaft
An open lift shaft in an active renovation zone acts as a highly efficient fireplace chimney. In a completed building, elevator shafts are engineered with fire-rated walls, pressurized containment systems, and draft-reducing vestibules. During structural refurbishment, these passive protections are absent or temporarily decommissioned.
When an ignition event occurs, the air inside the shaft is rapidly heated. Because hot air is less dense than the surrounding ambient air, it rises rapidly, creating a localized pressure drop at the base of the shaft. This pressure differential drives a continuous flow of oxygen-rich air into the fire's core, a phenomenon governed by the stack effect. The theoretical draft pressure ($\Delta P$) driving this vertical velocity is expressed by the equation:
$$\Delta P = C \cdot h \cdot \left(\frac{1}{T_o} - \frac{1}{T_i}\right)$$
In this equation, $h$ represents the height of the shaft, $T_o$ is the absolute outdoor temperature, $T_i$ is the absolute indoor temperature, and $C$ is a constant adjusting for friction and air density.
As $T_i$ rises exponentially during a fire, the pressure differential escalates, accelerating the velocity of superheated gases and smoke up the shaft. This draft pulls flames from the lower floors directly into the building's core, transforming a localized room fire into a multi-story conflagration within minutes. In the Brussels incident, this vertical propagation allowed the fire to travel down to the second basement level, trapping workers in a system that had become a vertical furnace.
The Structural Vulnerability Gap: Active Build vs. Completed Asset
The transition period between a building's strip-out phase and its final fit-out represents a period of maximum vulnerability. Completed commercial high-rises rely on a system of compartmentalization to survive fires.
In an active renovation site, this system is completely dismantled:
- Absence of Passive Barriers: Fire-rated drywall assemblies, intumescent seals, and self-closing fire doors are often removed or propped open to allow the movement of tools and materials.
- Fuel Load Characteristics: Renovation sites accumulate high volumes of transient combustible materials, including exposed insulation, wood framing, packaging, and chemical solvents.
- Decommissioned Active Systems: Wet-pipe sprinkler systems and smoke detection grids are typically offline or isolated to prevent accidental discharge or dust-triggered false alarms.
- Aerosolized Particulates: Cutting, grinding, and welding generate fine particulate matter that can accelerate flame propagation through the air.
This lack of containment means that any localized ignition has immediate access to unlimited oxygen and a high-energy fuel supply, with no physical barriers to restrict its spread to adjacent zones.
The Fallacy of Mechanical Transit During Thermal Events
The discovery of several casualties within the elevator cabins at the OXY building underscores the danger of using mechanical hoists during a high-rise fire. In standard operating procedures for finished structures, occupants are instructed to avoid lifts. On active construction sites, workers frequently rely on temporary hoists or unfinished elevators to move rapidly between high vertical intervals.
This reliance overlooks three primary failure points of mechanical vertical transit in active fire zones:
1. Thermal Expansion and Structural Alignment
The guide rails and cables of a lift system are calibrated to tight tolerances. Direct exposure to the thermal energy of a shaft fire causes rapid thermal expansion of the steel components. This warping deforms the guide rails, causing the safety brakes to engage automatically or jamming the cabin mid-transit.
2. Electrical Grid Failure
Under fire conditions, electrical insulation melts, causing short circuits that trip localized circuit breakers or main distribution panels. Once power is cut, traction elevators without secondary emergency power units stall immediately. On active sites, temporary electrical infrastructure lacks the redundancy and fireproofing of permanent emergency generation networks.
3. Toxic Asphyxiation and the Chimney Core
Because the lift cabin resides inside the primary path of the thermal updraft, the car acts as a collector for toxic gases. Carbon monoxide and hydrogen cyanide accumulate rapidly inside the cabin, causing unconsciousness in occupants long before structural thermal failure occurs.
Tactical Safety Mandates for High-Rise Refurbishment
Preventing future mass-casualty events during structural retrofits requires moving beyond basic compliance checklists to implement strict physical controls on-site.
Horizontal and Vertical Compartmentalization
Temporary fire curtains or fire-rated draft stops must be installed at every entry point to active lift shafts. These barriers must remain sealed except during the physical passage of materials. Shafts not actively used for hoisting should be capped with non-combustible decking at regular vertical intervals to disrupt the stack effect.
Pressurized Refuge Zones and Temporary Egress
In high-rise renovations, at least one concrete stairwell must be kept clear of all construction debris and equipped with temporary, positive-pressure blowers. These blowers maintain a higher air pressure inside the stairwell relative to the rest of the building, preventing smoke from entering the escape route.
Isolated Hot Work Zones and Continuous Fire Watches
Any spark-producing activity must be performed within a designated zone cleared of combustible materials. A dedicated fire watch must monitor the area during the work and for a minimum of 60 minutes after completion, utilizing thermal imaging cameras to detect subsurface smoldering in walls or floor joints.
Real-Time Personnel Tracking
Site management must utilize active RFID or BLE-based tracking systems integrated into worker safety gear. During an evacuation, emergency coordinators must have instantaneous data showing the exact vertical and horizontal coordinates of every individual on-site to direct rescue operations efficiently.
The incident in Brussels serves as a stark reminder that safety protocols must scale alongside the physical vulnerabilities of a building during its most unstable state. Relying on rescue teams to navigate uncompartmentalized, burning shafts is a high-risk approach. The industry must mandate physical barriers and automatic draft-disruption systems during the construction phase to eliminate the chimney effect entirely.
