--- product_id: 41959850 title: "0841DX F-Seal 181 Duct Seal, Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray, Made in USA" brand: "red devil" price: "$185.29" currency: USD in_stock: true reviews_count: 13 url: https://www.desertcart.us/products/41959850-0841dx-f-seal-181-duct-seal-fiber-reinforced-water-based store_origin: US region: United States of America --- # Exceeds SMACNA Pressure & Sealing Classes Weather-resistant for indoor/outdoor use UL 181 A-M & B-M certified 0841DX F-Seal 181 Duct Seal, Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray, Made in USA **Brand:** red devil **Price:** $185.29 **Availability:** βœ… In Stock ## Summary > πŸ”§ Seal smart, save energy, and stay ahead of the curve! ## Quick Answers - **What is this?** 0841DX F-Seal 181 Duct Seal, Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray, Made in USA by red devil - **How much does it cost?** $185.29 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/41959850-0841dx-f-seal-181-duct-seal-fiber-reinforced-water-based) ## Best For - red devil enthusiasts ## Why This Product - Trusted red devil brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **Fast & Safe Application:** Low VOC, quick-drying formula keeps your workspace healthy and your project on schedule. - β€’ **Leak-Proof HVAC Mastery:** Fiber-reinforced formula guarantees airtight, energy-saving duct seals. - β€’ **Built to Brave the Elements:** Weather-resistant and mold-proof for reliable indoor and outdoor performance. - β€’ **Universal HVAC Compatibility:** Certified for metal, fiberglass, and flexible ductsβ€”one sealant to rule them all. - β€’ **Made in the USA, Trusted Worldwide:** Premium quality sealant that surpasses industry standards for lasting HVAC efficiency. ## Overview The 0841DX F-Seal 181 is a premium fiber-reinforced, water-based duct sealant made in the USA. UL 181 A-M & B-M certified, it ensures leak-free HVAC systems across metal, fiberglass, and flexible ducts. Its weather-resistant, low VOC formula dries fast and exceeds SMACNA pressure and sealing standards, delivering durable, energy-efficient performance for both indoor and outdoor applications. ## Description Red Devil F-Seal 181 is a premium fiber-reinforced water-based duct sealant engineered for superior performance in all HVAC systems. This versatile sealant is UL 181 A-M & B-M certified, making it suitable for metal, fiberglass, and flexible ducts. Its fast-drying, low VOC formula ensures quick application and safety in sensitive environments. F-Seal 181 exceeds all SMACNA Pressure and Sealing Classes, providing unmatched sealing capabilities for high, medium, and low-pressure HVAC systems. The durable, weather-resistant formula is perfect for both indoor and outdoor use, resisting mold, mildew, and UV damage. It contributes to LEED EQ Credit 4.1 and meets CA Dept. of Public Health Emission Requirements V1.1, 2011. This USA-made product offers excellent adhesion, flexibility, and can be painted after full cure. For best results, apply in temperatures between 40Β°F and 110Β°F, allowing 24-72 hours drying time before pressure testing. F-Seal 181 is your go-to solution for efficient, long-lasting HVAC duct sealing. ## Features - SUPERIOR SEALING: Fiber-reinforced formula ensures leak-free HVAC systems, improving energy efficiency and performance - VERSATILE APPLICATION: UL 181 A-M & B-M certified for use on all types of HVAC ductwork, including metal, fiberglass, and flexible ducts - INDOOR/OUTDOOR DURABILITY: Weather-resistant sealant withstands various conditions, making it ideal for both interior and exterior use - FAST-DRYING & LOW VOC: Quick application and reduced drying time, with low volatile organic compounds for safer use in sensitive environments - EXCEEDS INDUSTRY STANDARDS: Surpasses all SMACNA Pressure and Sealing Classes, ensuring top-quality performance for your HVAC systems ## Technical Specifications | Specification | Value | |---------------|-------| | Asin | B01I7JVUO0 | | Best Sellers Rank | #12,833 in Tools & Home Improvement (See Top 100 in Tools & Home Improvement) #48 in Hardware Sealers | | Brand Name | Red Devil | | Color | Gray | | Compatible Material | Fiberglass, Metal, Plastic | | Customer Reviews | 4.5 4.5 out of 5 stars (1,528) 4.5 out of 5 stars | | Global Trade Identification Number | 00075339003466 | | Included Components | Duct Sealant | | Item Dimensions | 7 x 7 x 8 inches | | Item Form | Paste | | Item Type Name | Water Based Duct Sealant, 1 Gallon | | Item Weight | 1 Pounds | | Manufacturer | Red Devil | | Material Type | Acrylic | | Model | 0841DX | | Number Of Items | 1 | | Part Number | 0841DX | | Style Name | 1 - Pack | | Supported Standards | UL 181 a-m, UL 181 b-m | | Surface Recommendation | Metal | | Unit Count | 128.0 Fluid Ounces | | Upc | 075339003466 | | Water Resistance Level | Water Resistant | ## Product Details - **Brand:** Red Devil - **Item Weight:** 1 Pounds - **Item dimensions L x W x H:** 7 x 7 x 8 inches - **Material:** Acrylic - **Style:** 1 - Pack ## Images ![0841DX F-Seal 181 Duct Seal, Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray, Made in USA - Image 1](https://m.media-amazon.com/images/I/718Qkc+7HiL.jpg) ## Available Options This product comes in different **Color, Size, Style** options. ## Questions & Answers **Q: Is the "F" in the bucket like a liquid (brushable) or more like a paste?** A: It's not quite like a paste but it's not liquidity either and doesn't drip so you can put it on thick. I love this stuff, not much of a odor as well. I used a cheap chip brush to spread it. **Q: I'm redoing all the flex ductwork (insulated kind) in a crawl space. should i use the d our f sealant ?** A: You could use either one. Both are perfect for what you are doing, but I would use the F-Seal because it has fibers in it. **Q: Is this safe to use and will it work on gas dryer duct work joints (inside the fittings and outside)?** A: Sorry, this should not be used on a dryer. It is for HVAC only. Thanks. **Q: How long do I need to wait before turning on the A/C after application?** A: Hi, you should wait 24 hours. Thanks.... ## Customer Reviews ### ⭐⭐⭐⭐⭐ Thick and goes a long way *by on Reviewed in the United States July 30, 2024* Used this to seal various parts of my air conditioning system. I applied to seams and screws on the air handler in the attic and also to all connections of the flex duct from the sheet metal plenum. The goal was to reduce as much air loss as possible.I removed the flex duct that was held on with duct tape and a screw. It was all installed around 35 years ago and I found old instructions that said to use duct tape which of course today you are not supposed to use duct tape for anything HVAC anymore. I used an old 2" paint brush. You really want one with stiff bristles because this stuff is thick maybe closer to joint compound consistency. I spread everywhere around each start collar really pushing the sealant into the cracks and leaving a thick layer. I put a liberal glob over any screwheads and spread across any places air might pass through such as seams.It was dry enough within an hour to not be pliable anymore but full cure says 24-48 hrs. For me, I was able to do the second coat for most except the thicker spots. I poured a little water into the jug which thinned it so I could get a better spread over the thicker parts and feather out the product. I was working in a hot attic and I found having a separate container with just water helped a lot since leaving the lid off obviously dries it out. Adding water back in seemed to restore even the drier bits along the sides of the jug. I used a putty knife to scrape it back in and it mixed back in to the rest of it easily. I assume after a full cure it no longer accepts water and creates a permanent moisture proof barrier. Otherwise what's the point.I also spread some on the neck of the start collar and then inside the duct so that when I slid the flex duct back over there would be a seal. This is what you're supposed to do. I then put a screw back in to secure the two together. You're not supposed to do that though, you're supposed to use a zip tie and tensioning tool but I didn't feel like spending the money on those things was necessary since the screws held fine all this time. I used paper backed, pressure sealing foil tape to wrap the flex duct and seal it to the collar. Using pressure you get a great seal so no air can get in or out. Another coating of this mastic over the taped edges and I was set. Simply pull the fiberglass back over the collar and against the plenum then pull the outer vapor layer over the insulation to the plenum and I was done.I also redid a bunch of the flex connections to the boots. The boots had riveted edges which could easily pass air through so I spread over all corners inside or out.I have a 5 ton system and with everything I did there is still half of the container left. I liked the white color because I was able to use it on the ceiling diffusers to seal any cracks without worry about the color. I don't know what else this stuff can be used on but I'm going to find out. ### ⭐⭐⭐⭐⭐ Easy to use, easy to clean *by on Reviewed in the United States November 15, 2021* I used this duct sealant to seal seams and joints on approximately 250 feet of spiral pipe and assorted fittings and blast gates on my workshop sawdust collection system. I had a multitude of pipe joints, and size transitions from 8 inch duct down to 4 inches, along with a myriad of bewildering elbows and gates.The item performed as advertised, spreading easily across seams and joints and providing an airtight seal once properly cured.I found the application easiest with a cheap chip brush-aka a worn out paint brush with all but the first 1/2 of bristles brush cut off. Between this and latex gloves, I managed to properly seal every joint (inside and out) on the first try. School of hard knocks tip: keep a bucket of water and an old rag handy-this stuff is capable of coating a rookie installer in a wonderful layer of sealing goodness. However, I found that working cleanly and efficiently drastically reduced the amount of after the fact cleanup necessary.The hardest part of this process for me was waiting 24-48 hours for the duct sealant to cure before testing/usage. I used a few incense sticks to test for leaks, using the smoke to test for drafts/leaks within the vacuum system.Bottom Line Up Front: it works well, cleans up easily, and is relatively inexpensive. I have 3/4 of the large pail left-for future expansion projects. ### ⭐⭐⭐⭐⭐ Nice thick sealant easily applied with brush and easy to clean up since water based. *by on Reviewed in the United States October 17, 2025* I needed a duct sealant for the A/C intake air box. The edges of the air box had separated and were in need of repair to keep contamination out. I initially had some flexible strips to close the crack and then sealed it thoroughly with the duct sealant. Nice and think, but still easily applied with a paint brush. Since it is water based, I was able to clean the brush (and myself!) with just water. ## Frequently Bought Together - Red Devil 0841DX F-Seal 181 Fiber Reinforced Water Based Duct Sealant, 1 Gallon, Gray, Made in USA - Pro Grade - Chip Paint Brushes - 12 Ea 2 Inch Chip Paint Brush Light Brown --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.us/products/41959850-0841dx-f-seal-181-duct-seal-fiber-reinforced-water-based](https://www.desertcart.us/products/41959850-0841dx-f-seal-181-duct-seal-fiber-reinforced-water-based) --- *Product available on Desertcart United States of America* *Store origin: US* *Last updated: 2026-07-07*