Hardcast 304137 Duct Sealant 11 Oz Gray Synthetic Latex

Product Description

The HARDCAST 304137 is a gray, synthetic latex paste duct sealant supplied in an 11-ounce cartridge. It is designed to seal joints and seams in forced-air duct systems, preventing conditioned air loss and maintaining system efficiency. The sealant applies as a workable paste and cures to a flexible, durable seal capable of accommodating minor vibration and movement within the duct assembly. It meets UL 181 B-M requirements and carries listings under UL (Canada and US), ASTM C731/D2202, EPA, FDA, and USDA standards, making it suitable for both standard HVAC and industrial applications. HVAC technicians and sheet metal contractors are the primary installers of this product.

This sealant is formulated for use on metal duct, fiberglass duct board, duct fabric, and flex duct. It is appropriate for residential and light commercial forced-air systems as well as industrial duct applications. The paste consistency allows brush or gun application directly to duct joints, longitudinal seams, and connection points. Its operating temperature range of 35 to 110 degrees F covers typical installed duct environments, including unconditioned attic and crawlspace locations during warmer months and cold startup conditions in colder climates.

Key Features

• Flexible cure accommodates minor duct vibration and movement after installation
• Mold and mildew resistant formulation for long-term performance in humid environments
• UL 181 B-M listed for use on flexible and rigid duct systems
• Meets ASTM C731/D2202 and carries EPA, FDA, and USDA compliance
• Cartridge format compatible with standard caulk guns for controlled application
• Suitable for metal duct, fiberglass duct board, duct fabric, and flex duct substrates

Compatibility

Designed for sealing joints and seams on metal duct, fiberglass duct board, duct fabric, and flex duct in residential, commercial, and industrial forced-air duct systems where UL 181 B-M compliance is required.

Installation Notes

Installation should be performed by a licensed HVAC technician or sheet metal contractor in accordance with local mechanical codes and SMACNA duct construction standards. Shut down the air handling system before applying sealant to ensure proper adhesion and to prevent uncured sealant from entering the airstream. Allow a full 48-hour cure time before returning the system to operation. Do not apply over wet, oily, or heavily contaminated duct surfaces, as adhesion will be compromised.

Technical Specifications

• Type: Paste, Synthetic Latex
• Color: Gray
• Container Type: Cartridge
• Container Capacity: 11 ounces
• Temperature Rating: 35 to 110 degrees F
• Setting Time: 48 hours
• Applicable Standards: UL 181 B-M, ASTM C731/D2202, UL (Canada and US), EPA, FDA, USDA

Standard Information

• Brand: HARDCAST
• Manufacturer Part Number: 304137