Fire Sealant and Fire Stopping Sealant: A Guide to Intumescent Sealant Applications

When fire spreads through a building, it exploits every gap, penetration, and joint in the structure's passive fire protection envelope. Services that pass through fire-rated walls and floors, cable bundles that route through compartment boundaries, and the movement joints between fire-rated elements all create potential pathways for flames and hot gases to bypass the compartmentation that the building's fire strategy depends on. Fire sealant, fire stopping sealant, and specifically the intumescent sealant category are the products designed to close these pathways, maintaining the integrity of fire-rated compartments at every point where the structure is penetrated or interrupted.

What is fire sealant and how does it work?

Fire sealant is a compound applied to joints, gaps, and service penetrations in fire-rated construction to prevent the passage of flames, smoke, and hot gases through those openings for the same period as the surrounding construction is rated to resist fire. The mechanism by which a fire sealant achieves this differs by product type:

• Intumescent sealant: the most widely used category, intumescent sealant contains materials that expand significantly when exposed to heat, typically at temperatures above 150 degrees Celsius. The expansion of the intumescent material fills the gap or penetration as the surrounding construction heats, sealing the opening against the passage of fire. The expansion ratio of quality intumescent products can reach 10 to 20 times the original volume, which is sufficient to close gaps created by the melting or burning of the service materials passing through the penetration

• Acrylic fire sealant: a water-based, paintable sealant suitable for sealing linear joints and gaps in fire-rated plasterboard and masonry construction. Acrylic fire sealants provide fire resistance through the composition and char behaviour rather than through intumescent expansion, and are appropriate for applications where the sealant does not need to accommodate service penetrations through the joint

• Silicone fire sealant: a flexible, high-temperature sealant appropriate for movement joints in fire-rated construction where thermal expansion and building movement require a sealant with elastic recovery alongside fire resistance

Where is intumescent sealant used?

Intumescent sealant applications in building construction cover the full range of penetrations and joints that fire-rated compartmentation must address:

• Cable penetrations: cable bundles that pass through fire-rated floors and walls create open pathways whose effective area can be substantial. Fire stopping sealant applied around the cable bundle and filling the annular gap between the cable grouping and the penetration sleeve seals the opening, and the intumescent properties ensure that if the cable burns away under fire conditions, the sealant expands to fill the void the cable occupied

• Pipe penetrations: plastic pipes that pass through fire-rated elements melt and burn under fire conditions, potentially leaving open penetrations. Intumescent collars or intumescent sealant applied around the pipe at the penetration point expand to close the aperture if the pipe melts

• Steel pipe penetrations: metal pipes, which do not melt but conduct heat, require fire stopping sealant around the annular gap between pipe and penetration to prevent flame and gas passage through the gap

• Linear joints: the joints between fire-rated wall panels, between walls and floors or ceilings, and the perimeter gaps at the edges of fire-rated partitions require fire sealant application to maintain the compartment boundary

• Service duct penetrations: ducts carrying ventilation, electrical trays, or other building services that pass through fire-rated compartments require certified fire stopping at the penetration point, which may combine intumescent sealant with fire-rated duct wrap or collars depending on the duct type and size

What standards govern fire stopping sealant products?

Fire stopping sealant products in India must be tested and certified under the relevant Indian Standards or internationally recognised standards that the building specification accepts. The key standard for fire stopping products in the building context is IS 15758, which addresses fire stopping systems including sealants, and the broader passive fire protection framework of the National Building Code. Intumescent sealant products specified for building use should carry third-party certification from an accredited laboratory, with test evidence for the specific configurations in which the product is intended to be used: the penetration size, the service type, the construction thickness, and the fire rating claimed.

How is fire sealant applied correctly?

Correct application of fire sealant and intumescent sealant is as important as the product specification itself. A sealant applied at insufficient depth, to a contaminated surface, or in a configuration not covered by the product's test evidence will not perform to the rated level under fire conditions. Key application requirements include:

• Surface preparation: the substrate must be clean, dry, and free of dust, grease, and loose material before sealant application

• Minimum depth: the minimum sealant depth specified in the product's test evidence must be achieved across the full width of the joint or penetration

• Backing material: for deep joints, a backing rod of the specified type must be installed before sealant application to control depth and prevent three-sided adhesion that would restrict the sealant's movement and compromise adhesion

Vijay Systems supplies fire sealant, fire stopping sealant, and intumescent sealant products for passive fire protection applications in commercial, industrial, and institutional buildings across India. Vijay Systems' fire stopping range covers intumescent, acrylic, and silicone fire sealant formulations with the test certification and application guidance that compliant fire stopping installation requires.