Why these projects are different
In an ordinary building a cable fire is a serious event; in a tunnel, a hospital ward or an underground station it is a different order of risk. Escape takes longer, patients may not be able to move without help, smoke has nowhere to go, and the systems that keep people safe, from ventilation and smoke extraction to emergency lighting and public address, depend on cables that run through the same spaces as the fire. Cable trays in these buildings are also heavily loaded, so a cable that is harmless on its own can contribute to a fire when bunched with hundreds of others.
Project specifications respond by asking for several fire properties at once. The exact combination is set by national rules, the operator's own standards and the project designer, and it varies by country and by circuit. What follows is how such specifications are usually built, so that a buyer can read them and plan sourcing; it is not a statement of what any given project requires. Confirm the requirements with the project engineer and the AHJ.
The layers of a typical specification
| Requirement | Typical test route | Why it appears | How it is stated |
|---|---|---|---|
| Low smoke | IEC 61034 | Keep escape routes visible | Light transmittance per test report |
| Halogen free | IEC 60754-1 and -2 | Limit acid gas, protect people and equipment | Halogen acid, pH and conductivity per test report |
| Flame spread in bunches | IEC 60332-3, often a demanding category | Stop fire running along loaded trays | Category per test report |
| Circuit integrity for life safety circuits | IEC 60331, BS 6387 CWZ or BS 8519 | Keep ventilation, lighting and alarms running | Standard and duration per test report |
| Reaction-to-fire class in EU buildings | CPR class under EN 50575 | Legal requirement for cables in scope | Class declared on the DoP |
In practice this often means two cable families on the same project. General power, lighting and control circuits use LSZH flame-retardant cables with good bunched flame results. Life safety circuits use fire-resistant cables with circuit integrity on top. The circuit schedule tells you which is which, and the quote should follow the schedule line by line.
Tunnels and metros
Road and rail tunnels and underground stations combine long cable routes, mechanical exposure and limited ventilation. Specifications commonly ask for LSZH sheaths on all cables in the enclosed sections, bunched flame tests because of the long trays and ladders, and circuit integrity for ventilation fans, emergency lighting, signage, public address and fire detection. Long routes also mean large cross-sections, heavy drums and armour in places where cables are exposed to damage, so the LSZH armoured constructions described on the armoured cables page often appear alongside fire-resistant cables.
Tunnel projects usually come with detailed delivery plans: drum lengths matched to section lengths, drum numbers tied to the cable schedule, and witness tests at the plant. These belong in the contract from the start, because drum lengths affect production and drum making, which typically takes 2-4 weeks for wooden drums.
Hospitals
Hospitals add a second concern to smoke: patients who cannot be evacuated quickly, and equipment that must keep running. Specifications commonly call for LSZH cables throughout patient areas and escape routes, circuit integrity for life safety and essential supply circuits, and in EU hospitals a high CPR class declared on the DoP for the main cable families. Data and communication cables in the same building follow the same logic, so LSZH indoor fibre and LAN cables are often specified too, as on our data centre and building construction application pages.
Illustrative example: putting the layers together
An illustrative, anonymised case shows how this plays out. A contractor for an underground station extension sends a circuit schedule with three cable families: LSZH flame-retardant power and control cables, fire-resistant cables for smoke extraction fans and emergency lighting, and LSZH fibre for the communication network. The desk splits the schedule into the three families, shortlists partner plants that already hold the reports for each family and size range, and finds that two sizes of fire-resistant cable have no report at the required duration. The contractor chooses between a new test before production and a nearby size that already has one, with the project engineer's agreement. The decision is made before copper is booked, not after drums arrive on site.
Pitfalls on infrastructure orders
Three problems recur on these projects. The first is a specification written as one sentence for every cable, such as "all cables shall be LSZH and fire-resistant". Read literally, it pushes general power circuits into fire-resistant constructions and raises cost and lead time without improving safety; read loosely, it lets a supplier quote flame-retardant cable for life safety circuits. The desk asks the project engineer to confirm the circuit-by-circuit intent before quoting.
The second is report coverage by size. A plant may hold circuit integrity and bunched flame reports for its mid-range sizes but not for the smallest or largest sizes on the schedule. Gaps need to be found early, because a new test adds time before production.
The third is consistency over a long delivery programme. Infrastructure projects often call off cable over many months. The compound, mica tape and plant set-up should stay the same across call-offs, so the desk records the materials on each batch and compares them with the reports on file. A change of compound supplier mid-project is treated as a change of construction until the plant shows that the reports still apply, and the client is told before the batch ships.
Sourcing these cables through the desk
- Send the circuit schedule: sizes, cores, lengths and the fire requirement per circuit.
- Map the families: the desk groups circuits by construction and test route and checks report coverage per size.
- Plan the evidence: reports, DoPs and any certificates are collected for the submittal before production.
- Agree tests and witnessing: routine tests per drum, and witness or independent tests where the contract asks for them; see the engineering projects page.
- Confirm drums and timing in writing: drum lengths, numbering and delivery sequence; typical wording is on the MOQ and lead time page.
Fire-resistant constructions are on the fire-resistant cables page. Send the schedule through the quote form, and the desk will return a family-by-family plan with the documents that support each line.