Fireproof putty, such as 3M Fire Barrier Moldable Putty Stix MP+ or NS Fire® Putty, is used to seal cable tray penetrations, providing up to 4 hours of fire protection while remaining flexible and re-enterable.

Types of Fireproof Putty

1. Moldable Putty Stix (3M Fire Barrier MP+)

• One-part, intumescent, re-enterable putty sticks that can be molded by hand to fill gaps around cable trays and penetrations .
• Provides up to 4 hours of fire protection in accordance with ASTM E 814 (UL 1479) and up to 2 hours per ASTM E 119 (UL 263) when installed in UL-listed wall openings .
• Produces a draft and cold smoke seal, reduces noise transfer, and adheres to most construction substrates including metal and plastic .
• Suitable for synthetic cable jackets and cable bundles, remaining pliable over time without crumbling . 2. Fire Barrier Putty Sleeve Kits (3M)
• Ready-to-install kits designed for new or retrofit cable penetrations through walls or floors .
• Tested up to 4 hours for fire-rated through penetration systems (ASTM E814/UL 1479).
• No gaskets required; sleeves can be split or hinged for existing cables and accommodate oversized openings .
• Ideal for high-traffic cable penetrations and both industrial and commercial applications . 3. NS Fire® Non-Setting Putty
• Solvent-free, flexible putty for fire barriers up to 4 hours, tested to EN 1366-3 and BS 476 .
• Designed to remain flexible, allowing thermal and mechanical movement of cables and trays.
• Compatible with metallic pipes, cable trays, and cable ladders, and contributes to acoustic isolation up to 65 dB .
• Suitable for large service openings and irregular shapes, maintaining fire resistance without affecting plastic or metallic components . 4. Envirograf Intumescent Putty
• Flexible intumescent putty for use around copper pipes, cables, and steel electrical trunking .
• Moisture-resistant and expands under heat to seal gaps, providing fire protection.

Application Considerations

• Opening Size: Ensure the putty fills the gap around the cable tray; for example, 3M recommends openings 1.5 inches larger than the tray on all sides .
• Fire Rating Compliance: Choose putty tested to UL 1479, UL 263, or EN 1366-3 standards depending on local code requirements .
• Re-Entry: Moldable putty sticks allow for future cable additions or maintenance without compromising fire protection .
• Compatibility: Verify that the putty is safe for the specific cable types and tray materials used.

Summary

For fireproofing cable trays, moldable intumescent putty sticks, sleeve kits, or non-setting putty provide effective fire and smoke barriers. They are flexible, easy to install, and maintain fire ratings up to 4 hours. Selection depends on the installation type, opening size, and compliance with local fire safety standards. Products like 3M Fire Barrier Moldable Putty Stix MP+ and NS Fire® Putty are widely used in industrial and commercial applications for reliable firestopping of cable trays.