Fire stopping of penetrations: sealants, foams, collars, pillows, blocks

What is a fire-resisting penetration seal?

Fire walls and fire-separating floors divide a building into fire compartments so that a fire does not spread beyond the compartment in which it started. But pipes, cables and ducts pass through these walls and floors, and movement joints and installation gaps remain between building elements. Every such opening is a potential breach. A fire-resisting penetration seal is an assembly that closes the breach and restores the fire resistance of the element at the point where it is penetrated.

A penetration seal is assessed against the same criteria as the fire-separating element itself: E — integrity (no passage of flames or hot gases), I — insulation (the unexposed side does not heat up beyond the permitted limit). As a rule, the fire resistance rating of a penetration seal must be no lower than that of the element through which it passes.

Penetration sealing materials and how they work

Fire protection sealants

Acrylic, silicone and latex compounds for sealing gaps around pipes and cables, as well as linear joints. Intumescent sealants expand when heated and close voids, while ablative ones absorb heat. Silicone grades remain flexible and are suitable for moving joints and wet areas.

Fire protection foams

One- and two-component foams quickly fill openings of complex shape. For cable penetration seals it is important to be able to cut into the foam and add cables. Ordinary expanding foam, even when labelled “fire-resistant”, is not fire protection unless there is an approved solution for the penetration.

Pipe collars, sleeves and wrap strips

Combustible plastic pipes soften and burn through in a fire, leaving an open hole through the element. A pipe collar — a steel casing with an intumescent insert — crushes the softened pipe when heated and closes off its bore. Wrap strips and pipe wraps work on the same principle and are convenient in confined spaces.

Boards with a fire protection coating

Mineral wool boards coated with an ablative or “hybrid” compound close off large openings with mixed services. Joints and gaps around the services are additionally sealed with a sealant from the same system.

Pillows, blocks and putties

Ready-made pillows and blocks are laid in the opening like bricks. They are easy to remove and replace when the cable route changes, which makes them a good choice for server rooms and plant rooms. Putties are used to seal small gaps and electrical back boxes and to fill the spaces between cables.

How to choose a system

  • Type of construction. A concrete or brick wall, a lightweight plasterboard partition, a floor — and its thickness. Many solutions are approved only for specific types and minimum thicknesses.
  • Type of services. Metal pipes (insulated or not, and with what insulation), plastic pipes (material and diameter), cables and bundles, trays, mixed penetrations.
  • Opening size. Small openings — sealant or putty; medium — foam or blocks; large — coated boards.
  • Required rating for E and I, as well as any smoke tightness and sound insulation requirements.
  • Movement. Movement joints need materials with a proven movement capability.
  • Conditions. Humidity, external walls, pipe temperatures.
  • One system per penetration. Materials from different manufacturers are not mixed in one seal: the fire resistance evidence covers a specific combination.

Common mistakes

  • Sealing penetrations with ordinary expanding foam or cement mortar without an approved solution.
  • No pipe collars on plastic pipes.
  • Sealant applied to insufficient depth, or without the mineral wool backing specified by the system.
  • Penetration seals opened up during repairs and left open.
  • No labels or records for penetration seals — at inspection it is impossible to prove what they were made with and how.

Materials from leading manufacturers

  • Hilti CFS-S ACR — Hilti — acrylic fire protection sealant for joints and metal pipe penetrations.
  • Hilti CFS-F FX — Hilti — fire protection foam for cable and mixed penetration seals.
  • Hilti CFS-C P — Hilti — fire protection collar for plastic pipes.
  • Hilti CFS-BL — Hilti — ready-made fire protection blocks for cable penetration seals.
  • Hilti CFS-CU — Hilti — fire protection pillows for temporary and permanent penetration seals.
  • Hilti CFS-CT — Hilti — coating for boards in medium-sized and large openings.
  • Nullifire FS702 Intumastic — Nullifire (Tremco CPG) — acrylic sealant for linear joints and penetration seals.
  • Nullifire FB750 Intubatt — Nullifire (Tremco CPG) — coated mineral wool board for reinstating the fire resistance of walls and floors.
  • Nullifire FF197 — Nullifire (Tremco CPG) — fire-rated polyurethane foam for linear gaps and door frames.
  • PROMASTOP-CC — Promat — coating for penetration seals and coated boards.
  • PROMASEAL-AG — Promat — intumescent sealant for cables and combustible pipes.
  • 3M Fire Barrier Sealant CP 25WB+ — 3M — latex-based intumescent sealant.
  • 3M Fire Barrier Water Tight Sealant 1000 NS — 3M — silicone sealant for moving joints and for penetration seals that must also be watertight.
  • 3M Fire Barrier Moldable Putty Pads MPP+ — 3M — intumescent putty in pad form.
  • Hilti CP 611A — Hilti — intumescent acrylic mastic for cable and pipe penetrations.
  • Hilti CP 601S — Hilti — elastic silicone sealant for movement joints and metal pipe penetrations.
  • Hilti CP 636 — Hilti — firestop mortar for medium and large openings with cables, trays and pipes.
  • Nullifire FS703 — Nullifire (Tremco CPG) — fire-rated silicone sealant for linear joints in walls and floors.
  • Nullifire FJ203 — Nullifire (Tremco CPG) — non-combustible rock fibre rope for static and movement joints up to 150 mm.
  • Hilti CP 680-P — Hilti — cast-in firestop device for plastic pipe penetrations through concrete floors.
  • Hilti CFS-SP WB — Hilti — sprayable water-based acrylic firestop coating for joints and curtain wall perimeters.
  • Hilti CFS-PL — Hilti — reusable firestop plug for round cable openings in walls and floors.
  • Hilti CFS-W SG — Hilti — pre-cut intumescent wrap strips for plastic pipe penetrations up to 160 mm.
  • Nullifire FP170 Intucollar — Nullifire (Tremco CPG) — stainless steel intumescent pipe collar for combustible pipes, up to 4 hours.
  • Nullifire FR230 Intucompound — Nullifire (Tremco CPG) — gypsum-based fire-stopping mortar for wall and floor penetrations, up to 4 hours.
  • Nullifire FS709 HP — Nullifire (Tremco CPG) — graphite intumescent sealant for pipe and cable penetrations, up to 4 hours.
  • Nullifire FP302 Intustrap — Nullifire (Tremco CPG) — graphite intumescent pipe wrap for combustible and insulated pipes, up to 4 hours.
  • PROMASTOP-FC MD — Promat — cut-to-size fire stopping collar for plastic pipes from 40 to 200 mm.
  • Hilti CFS-C EL — Hilti — endless firestop collar cut on site for plastic pipes 16–160 mm.
  • Hilti CFS-B — Hilti — graphite-based firestop bandage for insulated metal and plastic pipe penetrations.
  • Hilti CFS-CID — Hilti — cast-in firestop device for 32–160 mm pipes in concrete floors.
  • ROCKWOOL Conlit Pipe Collar — ROCKWOOL — intumescent pipe collar for 110–250 mm plastic pipes in walls and floors.
  • Nullifire FS704 — Nullifire (Tremco CPG) — hybrid fire-resistant sealant for linear joints, up to 2 hours, 25 % movement.
  • Nullifire FS719 HP Blue — Nullifire (Tremco CPG) — blue graphite sealant for CPVC sprinkler pipe penetrations, up to 2 hours.
  • Nullifire FZ400 — Nullifire (Tremco CPG) — compressible graphite filler for movement joints and cable trunking, up to 2 hours.
  • Nullifire FP220 Service Sleeve — Nullifire (Tremco CPG) — stainless steel intumescent sleeve for combustible pipes in walls, up to 2 hours.
  • PROMASTOP-W — Promat — intumescent wrap for plastic and insulated pipe penetrations, up to EI 120.
  • PROMASTOP-I — Promat — water-based intumescent coating for cable and pipe penetration seals with mineral wool batts.
  • PROMASTOP-M — Promat — cement-based fire-stopping mortar for cable and pipe penetrations, up to EI 120.
  • Hilti CFS-SL GA — Hilti — firestop sleeve for cable penetrations with twist-to-close smoke seal, up to EI 180.
  • Hilti CFS-TTS E — Hilti — preformed head-of-wall seal for drywall partitions, EI 120, joints up to 25 mm.
  • Hilti CP 618 — Hilti — non-hardening firestop putty stick for cables and metal pipes, up to 3 hours.
  • Hilti CFS-SP SIL — Hilti — silicone firestop joint spray for slab-edge curtain wall perimeter joints, EI 180.
  • HENSOMASTIK 5 KS viskos — Rudolf Hensel — ablative coating over mineral wool for floor movement joints, up to EI 240.
  • HENSOTHERM M 2000 — Rudolf Hensel — fireproof mortar for mixed cable and pipe penetration seals, up to EI 180.
  • Nullifire FV225 — Nullifire (Tremco CPG) — open-state cavity barrier for ventilated rainscreen facades, air gap up to 25 mm.
  • Nullifire FZ100 Fire Safe Zone — Nullifire (Tremco CPG) — graphite foam slab for planned and future service penetrations, up to 120 minutes.
  • Protecta FR Coating — Protecta (Polyseam) — ablative coating for stone wool in the FR Board system, up to EI 240.
  • Protecta FR Acrylic — Protecta (Polyseam) — intumescent acrylic sealant for penetrations and 10–30 mm joints, EI 30–EI 240.
  • Protecta FR Graphite — Protecta (Polyseam) — graphite intumescent sealant for plastic pipe and cable penetrations, up to EI 240.
  • Protecta FR IPT — Protecta (Polyseam) — elastic IPT sealant-adhesive for joints and penetrations, 25 % movement, up to EI 240.
  • Protecta FR CPVC Sealant — Protecta (Polyseam) — acrylic firestop sealant for CPVC sprinkler pipe penetrations up to Ø73 mm, EI 180.
  • Protecta FR Foam — Protecta (Polyseam) — fire-rated PU foam for linear joints in concrete and masonry walls, EI 30–EI 240.
  • Protecta FR Board — Protecta (Polyseam) — coated stone wool batt for large openings with multiple services, up to EI 240.
  • Protecta EX Mortar — Protecta (Polyseam) — fast-setting gypsum-based mortar for floor and wall penetration seals, up to EI 240.
  • Protecta FR Pipe Wrap — Protecta (Polyseam) — graphite intumescent wrap for plastic pipe penetrations up to Ø400 mm, EI 240.
  • Protecta FR Collar — Protecta (Polyseam) — graphite-lined steel firestop collar for plastic pipes up to Ø400 mm, EI 240.
  • Protecta FR Putty Cord / FR Putty Pad — Protecta (Polyseam) — non-setting putty: cord for small annular gaps and pads for socket boxes, EI 240.
  • Protecta FR Graphite Plate — Protecta (Polyseam) — self-adhesive graphite plate for electrical wall boxes in drywalls, EI 30–EI 120.
  • Protecta FR Service Transit — Protecta (Polyseam) — firestop sleeve for cables and pipes that allows later re-cabling, up to EI 240.

Frequently asked questions

Can a penetration be sealed with ordinary concrete?

For uninsulated metal pipes in solid construction, the design sometimes permits this. Cables, plastic pipes and insulated pipework need dedicated solutions: concrete does not compensate for the plastic burning away and does not fill the voids within bundles.

What is the difference between a pipe collar and a wrap strip?

A collar is a ready-made product in a steel casing that is fixed to the wall or floor. A wrap strip is an intumescent material that is wound around the pipe and set into the opening. The choice depends on the pipe diameter, the location and the approved solutions available.

Do penetration seals need labelling?

It is good practice and, increasingly, a client requirement. A label stating the material, fire resistance rating and installation date makes maintenance and inspections easier.

Can materials of different brands be combined?

This is not recommended. Fire resistance is certified for a specific system, and replacing one component makes the outcome unpredictable.