Fire wrapping is a specialized insulation system designed to encapsulate kitchen grease ducts. Because grease is a highly flammable fuel, an internal kitchen fire can reach temperatures exceeding 1000°C. Without proper fire wrapping, this radiant heat can ignite nearby electrical cables, timber, or plumbing in the ceiling plenum, spreading the fire through the building.
To meet BOMBA and BS 476 Part 24 requirements, a fire wrap must provide three levels of protection:
Stability: The duct supports and the wrap itself must not collapse during a 2-hour or 4-hour fire.
Integrity: The duct must prevent flames or hot gases from leaking out into the rest of the building.
Insulation: This is the most critical. The wrap must keep the "cold side" (the outside of the wrap) below an average temperature rise of 140°C. This prevents "auto-ignition" of materials touching or near the duct.
Modern fire wraps have replaced heavy, bulky traditional enclosures with thin, high-performance blankets:
High-Temperature Silicate Fiber: These blankets are typically 25mm to 50mm thick. They are flexible, allowing them to be wrapped tightly around rectangular or round ducts.
Encapsulation: The fiber is usually "foil-scrim" encapsulated. This prevents the fibers from shedding and protects the insulation from moisture and grease.
Bio-Soluble Options: Modern 2026 standards prioritize bio-persistent-free fibers, which are safer for installers and building occupants if the ceiling plenum is used for return air.
The primary advantage of professional fire wrapping is the "Zero-Clearance" rating to combustibles.
Space Saving: Unwrapped ducts require a massive air gap (up to 450mm) from any wooden or plastic materials. A certified fire wrap allows the duct to be installed directly against a wall or floor penetration.
Overlap Requirements: To ensure no "Heat Leaks," the blanket must have a minimum overlap (usually 50mm to 100mm) at all joints and seams.
Stainless Steel Banding: The wrap is secured using heavy-duty stainless steel bands spaced every 200mm to 300mm. Plastic ties or standard duct tape are strictly prohibited.
The point where the duct passes through a fire-rated wall or concrete floor is the most common point of failure.
Fire-Stopping: The gap between the wrapped duct and the wall must be packed with fire-rated mineral wool and sealed with an Intumescent Fire Sealant.
Continuous Wrap: The fire wrap must be continuous. It cannot stop at the wall; it must pass through the wall or be "flanged" against it using specialized fire-rated angles.
While some smoke spill ducts only require an "Integrity" rating (to stay airtight), kitchen ducts must have an "Insulation" (I) rating. Grease fires burn long and hot; without the insulation layer, the metal duct becomes a red-hot heating element that can melt structural steel or start fires floors away from the kitchen.
Tested System: Does the wrap have a valid SIRIM or international test report for the specific duct size?
Access Doors: Are the grease clean-out doors also fire-rated? (They must be covered with a removable "plug" of the same fire wrap).
Support Protection: Are the threaded rods and hangers also protected? (In 4-hour systems, the hangers must often be wrapped to prevent structural failure).
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