NU-CALGON 4.25 lb. Odor Neutralizer, White Gel

Highly recommend. My HVAC husband inserted the boxes in/near the air conditioning unit(s??), and the whole house is odor-free. Will purchase again, please do not change the product.

works well in my cold air return box.

Really like using these in a very humid environment.

Controls odors.

Disappointed. I don't notice a difference at all

Bought this from my local HVAC shop and it's so good I came here to make a review. The block itself has a scent and you might think "my whole house is going to smell like this." Wrongo. It gives a very fresh no-scent, like purified air. Similar to what the inside of an empty fridge might smell like. Just cold air smell. It's great. It's currently in one of my returns laying on its side in the duct work. I plan to move it to after the evap coil (there's an image on the box of this configuration) after a few days use.

While it works great for helping control malodors, it DOES NOT last 6 months. Lucky if it lasts 2 months. The smaller version (which is good up to 2 months) lasted 4 months. I bought 2 of the larger ones thinking, eh something wasn't right.. but figured #2 would last much longer. Nope got less than 6 weeks out of it. I decided to go back to the smaller block.. but now that one keeps getting delayed and not shipped. I'm not sure what's going on with the seller, but I needed this.. so now I got an ozone machine instead. Guess we will see if it works better.