EV chargers in underground garages: fire safety

Are electric cars a greater fire risk?

Available analyses do not show that electric cars catch fire more often than combustion-engine cars. The difference lies in how the fire develops: a damaged lithium-ion battery can go into uncontrolled heating (thermal runaway), burns for a long time, gives off large amounts of toxic gases, can be difficult to extinguish and may reignite after being put out.

In an enclosed garage, this makes the fire brigade’s job harder. That is why the aim of the design is not to “ban electric cars” but to limit risk on the charging installation side and give rescuers safe conditions to work in: the ability to cut off power quickly, clear signage and access to the charging bays.

What the fire-safety expert checks

In Poland, the design of a charging installation in an enclosed garage is approved by a certified fire-safety expert (rzeczoznawca ds. zabezpieczeń przeciwpożarowych). They assess whether the new installation worsens the building’s fire-safety conditions:

• Integration with active fire protection systems: the fire alarm system (SSP), manual call points (ROP) and the fire-fighter’s power cut-off switch (PWP).
• Compliance with the building’s division into fire zones — including how new cables pass through walls and floor slabs between zones.
• The location of chargers in relation to escape routes, exits and staircases.
• Compliance with the building’s fire requirements set out in its design and fire safety instructions.

Disconnecting charging on alarm

Once the fire protection system is triggered, the charging stations must be disconnected. In a building this is done globally — the chargers are switched off together with the entire fire zone, not one by one. In garages with a fire alarm system, the chargers’ power supply is usually cut automatically after an alarm, and independently of that it can be disconnected with the fire-fighter’s power cut-off switch.

Individual emergency stop switches at each charger are usually used for outdoor stations outside the building.

Where to install chargers in the garage

• Away from escape routes, exits and staircases — so that a car fire does not cut off the escape route.
• Preferably close to the garage entrance, where firefighters have easier access and smoke is removed more quickly.
• In places protected against impact from manoeuvring cars — e.g. with wheel stops or protective bollards.
• With signage for charging bays and switches that is clear to rescuers.

A safe electrical installation

Most charging-related hazards can be mitigated on the installation side. In a multi-space garage this means:

• Chargers (wallboxes) instead of charging from household sockets — an ordinary socket can overheat under load for many hours.
• Residual current protection for each point with DC fault protection — a type B RCD, or a type A RCD with 6 mA DC detection in the charger.
• Cables and protective devices sized for continuous load, plus load management that prevents the installation from being overloaded.
• Cable penetrations through fire-zone boundaries sealed with fire-stopping systems of the fire resistance required for the given partition.
• Post-installation measurements with a test report, and periodic inspections of the installation.

What it usually looks like in practice

In the vast majority of cases, the expert does not impose significant additional requirements on the building. The recommendations most often cover linking the chargers to the fire alarm system or the fire-fighter’s power cut-off switch, the location of the points, signage and an update of the fire safety instructions. Less often — additional firefighting equipment or changes to ventilation and smoke extraction.

The expert’s opinion and the approved design are also part of the documentation needed when the station is subject to inspection by UDT (Poland’s Office of Technical Inspection).

The scope of requirements depends on the specific building and current regulations — we confirm it individually after analysing the building.

Rules for garage users

• Charge only from dedicated chargers, without extension leads or adapters.
• Do not charge a car with visible battery damage or after a collision until it has been checked by a service centre.
• Report damage to charger cables, plugs and housings to the property manager.
• Do not block access to chargers, switches and hydrants.