Nucalgon Residential Odor Neutralizer

2024 UPDATE: We had a mysterious chlorine-like smell outside an upstairs bedroom. We checked the upper zone air unit and the trunk line, but couldn’t locate a source. We changed the ceiling registers and thoroughly cleaned the room and hallway. We were renovating the bathroom and checked its walls and subfloor (the bathroom is right next to the bedroom with the odor). The smell lingered. In desperation, we used half (because of limited space) of a Nucalgon block in the upstairs ceiling cold air return compartment. Within 24 hours, the mysterious smell was gone. I’m always surprised at the bad reviews that complain the product doesn’t leave a scent. It’s an odor ELIMINATOR, not an air freshener. There are plenty of other things that will mask odors. This actually gets rid of them. Nothing compares to it. 2016 UPDATE: We have now used these in both our home, our rental property, and my daughter's home. She has a large breed dog and says that it is the only thing that will keep her house free of doggie odors. One block will clear the average 1600-1800 SF home for about 6-8 months. The powder "evaporates" (dissipates) over time. We use it primarily in the summer, when damp smells seem to be at their worst and humidity increases musty smells. We buy them every year and place them in the cold air return vents. REMEMBER TO DUMP THE CONTENTS IN THE BOX AND THROW AWAY THE PLASTIC. If you keep the powder in the plastic packaging (as one of our tenants did), it will not work. Wishing you all fresh smelling homes! ORIGINAL REVIEW IN 2013: We have had an extremely rainy spring and summer in the southeast this year. Every time I went downstairs there was a lingering musty smell in the downstairs hallway, which is where our cold air return opening is located. We replaced the filter, vacuumed out the entire area, ensured the vapor barrier under the house was intact, and tried various air fresheners to get rid of the musty, moldy smell. We tried this product figuring we had nothing to lose (I was considering calling one of the companies that come in to restore an area after a fire or flood to see if they could determine the cause and fix it). When this arrived in the mail, I was underwhelmed, and didn't think it would work. It is just compressed powder in a thin cardboard box, wrapped in plastic. First of all, you have to open the plastic bag it comes in and dump all of the material back into the box. Perhaps the reviewers who gave it a low score didn't follow this step. Personally, I found it to be a strange way to prepare the product for use, but we followed directions, put it in the cold air return, replaced the grille, and figured we would be greatly disappointed. Within hours, I went down the stairs and didn't notice anything. Nothing. Then it hit me. The lingering, musty smell that had plagued us for months had disappeared. Completely. Totally. If you are looking for something that has a "throw", or smells like fabric softener, fruit, vanilla, or flowers, this is not for you. All this leaves behind is odorless fresh air. A side benefit is that shortly after you cook something like fish, or fried food that normally leaves an odor behind, the smell is gone within an hour. Like it never even happened. I don't know what is in it...but it works. If you have an odor issue in the entire house and you have a dual zone HVAC, you will need to get two of these. We are considering getting a second one for our upstairs unit, just so the upstairs smells as outdoor fresh as the downstairs. Great product so far! The carton says it will last in a 5 ton system for two months. I'll write a follow-on to let you know how long it lasts.

When you get this the smell is very very strong. Don't worry about that. Once it's attached within your blower unit (we have a heat pump) you don't smell anything (or at least I didn't) in the home. Might take some skills to securely mount the unit so it is in the air flow but doesn't come loose. I find it lasts around a year. Kitchen smells, dog smells, etc. are quickly gone after a few minutes of air movement. Works well!

Works great for units that have issues with smoking in them. I’ve bought this block about 8 times and stick them in the furnace to guarantee the smoke smell disappears.

So there was a smell I began to notice coming through my vents. The funky basement smell. I tried everything. Clorox, Odo-ban, baking soda, pine sol, vinegar down the drains... You name it, I tried it. I couldn't keep the smell away for more than a day or two. It always came back. I was at my wits end. I even called the HVAC experts who suggested the very pricey service of duct cleaning. Yeah, no thanks. I figured there had to be a better way than to spend hundreds of dollars and still not being sure that it would solve the problem. I definitely did not want to spray and scrub my basement down with chemicals every few days. My husband couldn't detect the funky basement smell, but he can smell the chemicals a mile away. And he hated it. Enter the Odor block. In my desperation, I was scrolling online and came across this product. I took a gamble and wow.... So worth it. Even if they're a bit expensive, the smell is GONE. I no longer wake up in the morning and step out into the funky musty smell in the hallway. It just smells clean. Perfectly clean, not overpowering chemical clean. Directions could've been clearer for women like myself though who do NOT want to tell their husbands that we're going to start putting things inside the furnace. The first block- I tried to make fit by squeezing it through the crack where the air filter goes, but I bought a second block when I finally realized where this block REALLY goes. Ladies, just open up the front panel on your furnace and voila. You're in. Open the box, take block out of plastic sleeve and slide the bare block back into the box. Place into your spacious furnace compartment and close the furnace panel. YOU'RE DONE. Now peace can be restored to your kingdom!!

This does not even mask odors, if you have a bad odor in your vent you can smell that and the unpleasant soap smell of this at the same time. Less effective than a car air freshener.

I am very impressed with this. In the hot and humid summer days, there was a slight smell in the house. I installed this in the return duct behind the filter. The change was noticed immediately. The air has a smell of crisp winter air. After coming home from work, the air in the house stays fresh. This is well worth the money.

I have a chain smoker in the adjacent unit and my new air handler sucks in smoke smell from the unit. I thought it would alleviate or at least mask the smoke smell but it didn't. It worked for few days but then had no effect. I have a 3-ton unit and the directions state one box should be effective but it wasn't. I think for musty smells or pet odors this would be fine but smoke odors are too much.