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.

UPDATE: This fan is still going strong! Over a year later with no drop in air flow. I checked with an anemometer. I'm an AC Infinity fan for life!This is a great little fan for grow tents!I have this in a Mars Hydro 2x2x5 tent, sitting on the top exhaust, blowing the hot air with no problems.When I first got it and plugged it in to test, I thought it was broken till I put my hand over the exhaust! It's that quiet at lower levels! Of course as you turn it up the noise level increases, but it is by no means over bearing or annoying. Just a soft whoosh.The included speed controller is extremely long and you shouldn't have any issues with finding a place to mount it.Also don't forget that this fan in comparison with others (vivosun I'm looking at you) will use substantially less power, less noise, and will probably last 100 times as long. Not kidding on that last one, go look at the reviews for Vivosun fans... Some people don't even get a month out if them!I don't know about you, but when it comes to my plants, I can't afford to lose a crop due to my fan dying and needing to wait for a replacement! Buy ONCE with good quality rather than multiple times with poor quality.

Using this in a 2x3 grow tent. Initial impression upon unboxing was - Quality! When I first installed it, I was impressed with how quiet it was but was expecting more negative pressure. I realized I had too many bends (including a 180) in my ducting, so I moved the tent around (now I have a 90 and three 45's) and got some wattage testing done at different settings. 50% power vents this tent now and it uses 6.3 watts and is nearly silent. 75% vents very well, is quiet, and still only uses 13.1 watts. At 100% power, it is overkill, a little loud, and provides too much negative pressure even with an active intake fan and passive intakes open... and that uses only 23.3 watts. At 50% it still provides negative pressure even with an AC Infinity 4" booster at full tilt as the only active intake (which is also a great fan but using 11.8 watts vs the Cloudline at 6.3 watts).If you have a smaller tent, this is all you will need for an efficient exhaust fan. It will efficiently scale up to accept a filter, a couple of bends in your ducting, and perhaps even a bigger tent. I wouldn't be surprised if it could do a 3x3 at full tilt.I looked at fans for a very long time before pulling the trigger on this one, and I am glad I did. I will likely be purchasing the upgraded "67" controller in the future.