The current situation: Plaster in fire protection
To this day, fire protection cabinets for tunnelling are built using plaster. These are made from plasterboard and completely clad with stainless steel. This sandwich construction makes it possible to fulfil the requirements for fire load insulation and functional integrity. Even if temperatures of up to 1,100 °C occur inside the enclosure during a fire in an electrical system, the temperature on the outside of such an enclosure may only reach 160 °C. And even in the opposite case of a fire on the outside of the cabinet, the air temperature inside should not exceed 100 °C.
Plaster is a very soft material that is easy to work with. At the same time, this material contains a relatively high proportion of bound crystallised water. This is released as water at temperatures above 163 °C. The result is the slow dissolution of the already soft plaster structure. Another aspect restricts the use of plaster in tunnelling: plaster is hygroscopic. Water is therefore absorbed from the surrounding air. The consequence of this is the formation of mould.
Plaster-free fire protection – swibox IOP-Enclosures
swibox has specialised in the design and construction of cabinets and enclosures for tunnel construction for many years. In collaboration with the BFH (Bern University of Applied Sciences) and selected project partners, the Swiss company has looked for an alternative to the widespread use of plaster and is now presenting a comprehensive range of innovative fire protection enclosures in the form of IOP enclosures. The IOP enclosures are based on cement-bonded fire protection boards that are also reinforced with glass fibre.
Just like plasterboard, these fulfil all fire protection requirements. However, they are much more stable and resistant to moisture and its consequences. These Aestuver® boards are extremely stable, but also much more difficult to process. The challenge was therefore to optimise the processing of the material. The result is a product series within which customised, tailor-made sizes in different variations are possible.
As there is no need for a complete stainless steel cladding, IOP-Enclosures are much cheaper. This is a compelling argument, especially in times of ever-increasing cost pressure – even in tunnelling.
Plaster fibre fire protection board
- Non-combustible A1
- Easy to process
- Surface finishing with wood or plastic coatings
- Very well suited for drywall construction
- High proportion of crystalline bound water
- Hygroscopic (attracts water)
- Bulk density > 1500 kg/m3
- Heat-resistant up to 650 °C
- High load-bearing capacity due to cellulose fibres
- Must be fully clad with stainless steel 1.4404 / 1.4571 when used in tunnels
Cement-bonded fire protection boards (Aestuver®)
- Non-combustible A1
- Fire protection boards are frost, water and weather resistant
- Can be cleaned with a high-pressure cleaner
- High abrasion resistance
- Glass fibre reinforced lightweight concrete panels
- Bulk density > 965 kg/m3
- Good insulating properties thanks to incorporated glass beads
- Easy to produce customised sizes
- Fulfils the requirements for tunnel construction
IOP-Enclosure in detail

Hinges adjustable
Hinges made of stainless steel
Plastic or stainless steel closure
Detachable door
Stainless steel edge protectors

Easily accessible locking mechanism
Detachable door
Silicone seal for IP protection
Fire protection
seal foamed on
Reinforcing plate for wall mounting
Mounting point for mounting plate
IOP-EI90 wall-mounted enclosure
Maximum dimensions
Inside H 1200 x W 600 x D 400 mm
Outside H 1310 x W 710 x D 470 mm
Minimum dimension
Inside H 300 x W 300 x D 200 mm
Outside H 410 x W 410 x D 270 mm
Enclosure
Protection class: Up to IP 54
Protection class: I
Impact resistance: IK10
Ambient temperature: -25 °C +40 °C
Colour code: Concrete look
Enclosure: Halogen-free, non-flammable A1
Edge protection: Optionally made of stainless steel (1.4404; 1.4301) or according to customer requirements
Connecting elements made of stainless steel
Fittings made of stainless steel 1.4404
Assembly
- Pre-drilled mounting bracket Ø 13 mm
- M8 threaded bolt to hold the mounting plate, concrete screws
Locking
- Two and three-point rod lock Swivelling lever handle, profile half cylinder, Euro cylinder and other inserts as accessories
Door
- 180° opening angle, flush-fitting and fitted with all-round fire protection seal
- Silicone seal prevents water and dust ingress
- Hinges are adjustable
IOP-EI90 floor-standing enclosure
Maximum dimensions
Inside H 2000 x W 600 x D 800 mm
Outside H 2130 x W 730 x D 870 mm
Minimum dimension
Inside H 1400 x W 250 x D 200 mm
Outside H 1530 x W 380 x D 270 mm
Plinth
Height 100 mm, can be driven under
Enclosure
Protection class: up to IP54
Protection class: I
Impact resistance: IK10
Ambient temperature: -25 °C +40 °C
Colour code: Concrete look
Enclosure: Halogen-free, non-flammable A1
Edge protection: Optionally made of stainless steel (1.4404; 1.4301) or according to customer requirements
Connecting elements made of stainless steel
Fittings made of stainless steel 1.4404
Adjustable plinth feet
Assembly
- Pre-drilled mounting bracket Ø 13 mm
- M8 threaded bolt to hold the mounting plate, concrete screws
Locking
- Three-point rod lock Swivelling lever handle, profile half cylinder, Euro cylinder and other inserts as accessories
Door
- 180° opening angle, flush-fitting and fitted with all-round fire protection seal
- Silicone seal prevents water and dust ingress
- Hinges are adjustable
Approvals and tests
- Fire protection panels ETA-11/0458
- Tested according to EN 62208 Empty enclosure standard
- Tested according to EN 1363-1 Fire resistance up to EI90
- Cleaning test with high-pressure cleaner
- Arc test according to DIN VDE 030 Part 5