Is Flex Seal Safe for Ductwork? A Comprehensive Guide

The Flex Seal 450 is a locking system specifically designed for use in flexible air connections and ducts. It is a flame-resistant and temperature-resistant product that can protect against the spread of smoke and dirt. Many business owners are turning to Flex Seal to prevent fiberglass emissions due to outdated and damaged insulation. It is a water-based product that dries quickly and does not produce odors, making it safe for use in HVAC systems.

According to the hazardous materials identification classification, Flex Seal has a low HMIS hazard rating, meaning it poses little or no threat to health. Regular duct tape should not be used in ducts, as it is not UL certified and won't hold on for long. Instead, you should use a special tape with an aluminum backing that resists temperature changes or putty, a sticky adhesive applied with a spatula. The Flex Tape website mentions air conditioning systems as common surfaces on which its products are used, but they also manufacture specific tapes for use in ducts.

The result is that Flex Seal applies easily and seals well, but it doesn't seem to be as flexible as other products. If you need help from an expert, K&M Facility Services of AZ are the professionals when it comes to applying sealant and maintaining your HVAC system. The Mythbusters discovered that duct tape can seal leaks when applied dry, not in water. However, Flex Seal covered the surface well but cracks in the joints of the sheet metal reopened their way through telegraphed.