AC InfinityCLOUDLINE PRO S4, Quiet 4” Inline Duct Fan with Speed Controller – EC Motor Ventilation Exhaust Fan for Heating Cooling Booster, Grow Tents, Hydroponics

This is my third, and likely last, exhaust fan I've bought for a project. I wanted an exhaust system for our cat's litter box cabinet so that it would create a small amount of negative pressure and pull the bad odors outside. This fan is absolutely perfect in every possible way and has far exceeded my expectations. I arrived at this fan, after purchasing two others that were just too loud, as the noise seemed to bother the cat.I installed 2" PVC in the wall behind where the cabinet is, because I needed something small enough to fit. I then had a 90 degree elbow coming out of the wall, through a cover plate and then going into the back of the cabinet. In the attic, I installed a 2" to 4" duct adapter onto the 2" pipe, ran 25' of flex duct to this fan, and then another 16' run of duct to the roof vent.While the first two fans where very noisy, even at the lowest speeds, this one is virtually silent. I'm running it on level 2 and cannot hear anything inside the cabinet or in the house. Since I'm restricting the intake to only 2", anything above level 2 would likely just be a waste of power. This setup is working perfectly and creates more than enough exhaust to do the job and it does it in silence. The prior fans moved the air ok but had a really annoying hum that could be heard through the ductwork and also inside the house through the insulated ceiling. I hear nothing with this one.In addition to the above, the fan is rock solid and came with EVERYTHING one could possibly need to install it, including hose clamps. It's almost overkill but shows attention to detail. It also came with a very nice instruction book (yes, it's a substantial book) with detailed instructions on every aspect of installation and operation.The speed controller is very nice and easy to use. I just set it to my desired level and forget it. It will remember its current setting and resume after a power outage.This fan cost a bit more but is absolutely worth every penny paid. The difference in quality and quietness cannot be matched. I could not be happier, cat is happy, and we have an odor-free home.

I bought this duct fan to help expel the fumes from my 3D printer outside, and it’s been a fantastic addition to my setup. It runs 24/7 on the lowest setting, providing continuous ventilation, and I only need to turn it up when actively printing. Despite the constant use, it’s quiet, effective, and has been completely reliable—no issues whatsoever.The fan is compact, which is ideal since it doesn’t take up much space in my setup, making it perfect for those using a vented enclosure for safer 3D printing. The button controls are also very easy to use; however, it can be a bit annoying if you accidentally skip over a level since you have to cycle through again—you can’t go directly backward.If you’re looking to maintain good ventilation and control fumes in your workspace, this fan is an excellent choice.

Replaced multiple bathroom fans in my house with several of these. Everything about it feels premium. The packaging is nice, the hardware feels like it could be mounted on an aircraft, speed control is smooth, it remembers the speed you set it on even after a power interruption (meaning you can control it from a regular wall switch without loosing your preferred setting), and I've had one in my 120*F texas attic running 24/7 for more than two years and it hasn't missed a beat - and most importantly is still quiet. No rattling or squeaking. This is the one to buy. Worth every penny. And costs less than the "quiet" bathroom fans at home depot, is quieter, and moves more air. If your attic is accessible it's a piece of cake to cut it in line with the duct and hijack the power going to the original fan. Takes less than an hour per bathroom to retrofit for someone with DIY experience and some hand tools.

I bought this fan as a way to vent a custom enclosure with carbon filters. To my pleasant surprise this fan runs extremely quiet for the amount of air it moves. Even at the highest setting I was surprised. It's not dead silent but it's quieter than I've experienced with other fans.The ducts are not included but fit well. Any 4" duct works will do.Setup is extremely easy. At first I thought I would need to finagle around to get this mounted to the wall. The metal brackets however allow you to remove the center fan with extreme ease. After that you just mount onto your target area, in my case the wall, then reattach the fan. Be careful with the washers and nut if you do unscrew the metal claps completely. They're hard to find after. I lost one of the washers and am still looking for it. While that's not ideal it is working fine without it.The controller for this was simple too. You click the button to increase the speed of the fan. After you reach the end, the device shuts off. There's a nice mount option on the back of it too.