Best Quietest 4 Inch Inline Fan

Have you ever anticipated purchasing something but when you finally do, it shatters your heart to pieces? Well, this happened to me a year and a half ago when I bought a fan (just because it was an inline fan) only to end up disappointed with the noise.

The excuse was because I had never purchased an inline fan for the house myself. Even with this excuse, I still needed to get a fast solution to the disaster of a fan purchased as it made the house almost inhabitable.

As I launched my search for a quiet 4-inch inline fan, I realized that it was not easy and I swore that I would make it as easy as possible for others. This is why I have simplified the search for you to the best five quiet 4-inch inline fans.

The Quietest 4 Inch Inline Fan Comparison Table

Factors to Consider When Shopping for the Quietest 4-Inch Inline Fan

Now that you are aware of the best 4-inch inline fans in the market, it is important to understand the factors that you should look out for when purchasing them.


Purchasing items blindly can be quite costly in the long run and you do not want a quality inline fan that does not fit your personal needs. One of the important facets to consider is the airflow rating of the inline fan.

There are those with low ratings while others have high ratings. An example would be our TerraBloom 4″ 188 CFM and the TerraBloom 4″ 100 CFM mentioned above.

Finding the CFM rating you need is quite easy. It only requires measuring a room to determine the square footage and then looking at the CFM rating of the 4-inch inline fan. The recommendation from the home ventilating institute is one CFM per square foot of space. The minimum CFM of an inline fan is 50 CFM.


The ability to install the fan is a critical point of consideration. The COVID-19 season especially has taught us how important it is to purchase products with ease of installation given that movement is supposed to be minimal.

It is sometimes a waste of time to have someone come to install something like an inline fan. Thus, select a fan that has instructions on installation and also one that has brackets eases the struggles of outsourcing the service whether to volunteer or paid parties.

You do not want an inline fan whose noise would drive you crazy which necessitates considering the amount of noise that the inline fan emits. This is unless you are getting a fan that will be of use far away from living spaces. 

Energy Efficiency

It is also important to consider the amount of energy used by the fan. It would be an added burden to have exceedingly high bills after installing an inline fan.

Prior to purchase, look at the options that have features that could help in additional energy savings. Some of the features to look out for in these fans include their motion sensing and humidity sensing capabilities.

Motion sensing fans automatically turn off when a person leaves the room. There is no need to worry that the above recommended inline fans do not have this capability.

The motion-sensing capability is most appropriate for space where the inline fan is only in use under supervision where most of the recommended fans are left to work on their own. The humidity sensor detects humidity and then automatically turns it on. 

Adjustable Speed

Unless the inline fan works well at all speeds such as the Soler & Palau TD-100XS In-line Exhaust Fan, it is critical to consider whether the fan comes with adjustable speeds. Although it is easy to purchase a fan speed control and install it, it may not be part of your budget.

Additionally, there are some inline fans that do not have the provision of adding an external control. This leaves you stuck with only the switching on/off button and a speed that you would prefer to increase with no option of doing so. 

Safety Tips When Buying the Best 4 Inch Inline Fan

As much as having a 4-inch inline fan is beneficial for users, it can lead to some safety problems if mishandled. This is an occurrence that is easy to prevent with the right safety tips and precautions.

On top of the list for these safety precautions, is to ensure that the fans are kept out of the reach of children. Unsupervised children can pull the ducts, insert items on the rotating blades which are all recipes for disaster. Away from children, ensure that you also do not pull the ducts or insert objects on the rotating blades. 

It is also critical that you use the fan for air exchange purposes only to prevent any accidents. It is very tempting to disassemble the fan especially when it has a faulty that seems ‘fixable’. However, avoid disassembling, repairing, or modifying the fan without an expert by your side as it may lead to electric shock, fire, and fan failure.

Lastly, ensure that you do not use the fan where it may be subject to flammable or explosive gas as it can lead to injury and massive losses.

Best Quietest 4 Inch Inline Fan

1. TerraBloom 4″ 188 CFM Inline Duct Fan with Variable Speed Controller

The TerraBloom 4″ 188 CFM is one of the best inline duct fans one could ever possibly purchase if experiencing any air exchange issues whether indoors or outside in a grow tent. It has an output of 188CFM which facilitates efficient airflow. 

It is also an extra quiet device which is appropriate for people who are using it in spaces with other activities happening that do not require much noise. If you are wondering about the cost, this product is quite cheap considering all the benefits it will introduce to your spaces.

This product also reduces the headache of the user as much as possible first due to its easy installation. One does not need a professional or an experienced individual for installation or unmounting as there is a mounting bracket that is easy to use. Additionally, it also has a built-in adjustable speed controller making it easy to regulate the fan.

The limitation of this fan is that there is a possibility of leaking from the seals that is irritating for people using it to exhaust steam in a room. Apart from this, it is a fan worth exploring that would forever change your spaces.


  • Easy to set up even for non-experienced individuals
  • A strong output of 188CFM
  • Adjustable speed controller (built-in)
  • Extra quiet
  • Cheap


  • Possibility of leaking from the seals

2. TerraBloom 4-Inch 100 CFM Inline Duct Fan

The first thing that would have one wondering is the difference between the TerraBloom 4-Inch 100 CFM Inline Duct Fan and the TerraBloom 4-Inch 185 CFM Inline Duct Fan. They are similar to the same company only that the 100 CFM works efficiently for smaller spaces. 

Nobody wants an inbuilt duct fan that will have so much noise that would drive one crazy. Luckily for the TerraBloom 4-Inch 100 CFM Inline Duct Fan, there is a quiet operation meaning that worrying about noise will be something in the past. 

Installation of fans can be a nightmare. This need not be an area of worry as installation and unmounting the fan is quite easy. It is also relatively cheap compared to other models. Durability and sturdiness are also among the critical components when purchasing a fan. 

You do not want to purchase a fan and then rush back to the stores after a short while. I can assure you that this fan is durable. However, for more than assurance, the fan comes with a one-year warranty which I am almost certain you will not need.

The lack of a built-in speed controller should not serve as an impediment to the purchase of this great fan. It will surpass your expectations considering that it is quite cheap and does the job efficiently. 


  • Quiet operation
  • Easy installation and unmounting
  • Relatively cheap compared to other models
  • Durable with a one-year warranty


  • No inbuilt speed controller

3. Soler & Palau TD-100XS In-line Exhaust Fan

Soler & Palau TD-100XS In-line Exhaust Fan
  • Class I electrical insulation IP 44 Protection Thermal Overload Protection Class B Motor Insulation Sealed for Life
  • Safety tested by Underwriters Laboratories, Inc. and are UL and cUL Listed. ETL Listed
  • 4'' or 5'' Inline mixed flow duct fan-H: 203 cfm, L: 108 cfm

When purchasing a product for the first time, people want insurance and peace of mind and this is exactly what this fan provides. It has a five-year warranty which also serves as a reminder of its great quality. After all, the manufacturer would not give such a long warranty if they were not sure of its quality.

The machine is strong and provides pristine air conditions within your spaces. The fact that it works well on all speeds also lessens the bother of regular adjusting of the speed. It will work great even at the lowest of speeds.

With this fan, noise will be a thing of the past as it is extra quiet. The fan also has the benefit of a smooth airflow due to its high CFM rating. Installation is not a problem for the Soler & Palau In-line Exhaust fan as it comes with mounting materials and is easy to attach and detach from the wall. 

The only limitations of the fan are that it is bulky and more expensive than other models of inline fans. However, with its massive benefits, it is possible to overlook these minimal discrepancies and get a Soler & Palau In-line Exhaust fan for your space today! 


  • Easy to install and unmount
  • Extra quiet!
  • Works well on all speeds
  • Sturdy design
  • High CFM rating
  • Five-year warranty


  • Bulky than most other inline fans
  • Expensive than other models

3. Hydrofarm Active Air 4 inch in-Line 165 CFM Fan

Hydrofarm Active Air 4 inch in-Line 165 CFM Fan,...
  • Active Air inline Duct fans offer innovation & performance at a great price.
  • Active Air inline Duct fans incorporate Brushless thermally protected AC motors with sealed for life bearings (will not require any lubrication).
  • With a full line of fans to meet your needs, all Active Air Fans feature: Durable ceramic-coated metal housing, UL-recognized components, High quality molded impeller, Low noise output, Includes mounting brackets and 8 foot pre-wired 120V cord.

The word is already out that Active Air produces some of the best inline fans in the industry and the Hydrofarm Active Air 4 inch in-Line is no different.

The in-line fan is made to produce low and very tolerable noise for any space whether a bathroom, grow room, and even kitchen. On color, I am a little biased because of my love for green but I think it’s a beautiful addition to any space not forgetting its sleek design.

The fan is also high quality and durable with a one-year warranty (don’t dismiss this)-after all, there are inline duct fans that have no warranty. The 165 CFM is also high enough to ensure efficient airflow in any space. 

When it comes to inline duct fans, trust me that you do not want a machine that is prone to rust. It is pathetic, to say the least. The ceramic coated housing takes care of this concern increasing the attractiveness of this product. It is also super easy to install!

The drawback is that it does not have a built-in adjuster and is more expensive than comparable models. These are limitations for which solutions are easily available and thus should not hinder you from purchasing this life-changing product. 


  • Low noise
  • High CFM (165)
  • High quality and durable
  • Housing inside ceramic coating
  • Beautiful color and sleek style


  • No built-in speed adjuster
  • Expensive than comparable models.

4. iPower GLFANXINLINE4 4 Inch 190 CFM Inline Duct Ventilation Fan

iPower GLFANXINLINE4 4 Inch 190 CFM Inline Duct...
  • Specifications: diameter: 4inch; Air flow: 190 CFM; Speed: 2460 RPM; Wattage: 74W; Noise level: 65dB. 110V standard household plug; Pre-wired 5 Feet power cord.
  • Durability: durable ceramic-coated can resist atmospheric corrosion from humidity. Tight and precise construction reduces wear and tear to give the element a long life. Permanently lubricated bearing that requires zero maintenance.
  • Advantages: remove heat from the system to solves air delivery problems without major system rework or expense. Suitable for industrial, household and horticulture ventilation applications for air clean and temperature control.
  • Easy to install: the installation process only takes a few minutes. Tip: The maximum ambient temperature is 176°F/80°C; Without speed controller.
  • Package including: 1 pack 4inch 190 CFM inline duct ventilation fan.
  • Power source type: Corded Electric

There is nothing as great as purchasing something and then it surpasses your expectations. This is exactly what this little powerful machine does with its massive benefits.

First, you do not have to worry about the rust that affects durability because the inline duct fan has a ceramic coated housing.

In case you want to get better assurance, the product also comes with a one-year warranty (trust me you won’t need it!). It is one of the few inline ducts that come with a carbon charcoal filter meaning that it can filter out odors, chemicals, smoke, and fumes in an instant. You do not have to incur additional costs of purchasing a carbon charcoal filter.

Ease of installation is a top priority for most inline duct purchasers and this item provides that. It has an all-in-one kit which contains all instructions for installation. Most of us hate ductwork and the good news is that there is no ductwork needed for this fan.

Users have complained that the fan motor may be noisy- a tolerable level of noise after a few months of use. Tolerable noise is just a needle in a haystack of benefits. So you can go right ahead and purchase this wonderful equipment for your spaces!


  • Ceramic coated housing
  • Easy installation and unmounting
  • One-year warranty
  • Carbon charcoal filter
  • No ductwork needed


  • The fan motor may be noisy (tolerable noise) after a few months of use


If you are looking for good airflow within your spaces, without the high and disturbing noise, then the 4-inch inline fan is one of the best decisions that you will make.

There are so many in the market but the five narrowed down above are the best and quietest. I recognize that making a decision is one thing and an informed decision another. The latter is what you will make with this guide.

I am positive that you are on your way to getting the best 4-inch inline fan and maximizing its use with this guide. Don’t forget to take your time before purchasing to get the best possible device for your needs!

Other Related Inline Fans

Quietest 6 Inch Inline Fans

Quietest 8 Inch Inline Fans