Duct sealant is a soft compound that is often compared to mass. It is designed for ease of use and installation, and was originally developed for HVAC purposes. Duct sealant is used to create a seal that blocks moisture, dust, and air movement and can also block noise. This material is non-conductive, non-corrosive and will never dry out, allowing it to be easily removed, reshaped and reapplied whenever necessary.
While duct sealant is designed to repel moisture, it is primarily used to seal air leaks rather than plumbing leaks. Therefore, it has somewhat limited plumbing applications and is most often used to repair air ducts and for other electrical or HVAC purposes. However, the plumber may use duct sealant when working with an appliance such as a washing machine, refrigerator, or dishwasher, since duct sealant can be used to protect areas with electrical connections or to ensure that outlets and switches are safe from nearby water sources. It can be easily worked by hand to form an infinite variety of shapes that are pressed to seal HVAC ducts, hence its name as duct putty. Rainbow Duct Seal putty is primarily used by construction and specifically by the electrical industry to seal electrical boxes, service mast covers and entrances, etc.
When combined with shrinkage and sagging factors, the performance figures of duct putty joints, which start out relatively weak at first, tend to go only in one direction over time. Duct putty is undoubtedly the most used product for sealing electrical and telecommunications ducts worldwide. The cost of premature cable failures, damaged electrical appliances, damaged telecommunications equipment, ruined carpets and floors, and even stained drywall as a result of faulty duct seals should be a major factor in this analysis. In the case of duct putty, the UL mark is generally for sealing junction boxes, not for duct entrances that contain electrical or communication cables.
UL-rated duct seals are often classified based on the surface combustion characteristics of general-purpose tapes. Suffice it to say that today very few of the vitally important pipelines in nuclear power plants are sealed with pipeline putty. Duct putty is commonly used to seal electrical and communication ducts around the world, but it falls far short of expectations. Another important consideration is the performance of a putty duct seal that would otherwise be intact and that has not yet sunk or cracked.
Ultimately, the solution consists of specifying alternative sealing products that meet the performance parameters suitable for the installation, such as closed cell foams or mechanical seals.