Are you looking for the best 4-inch inline fan, exhaust fan, or duct fan for your grow room? You’re in the right place.
Airflow and circulation are just as important as your light source, growing media, water, and nutrients, but one thing makes it the hardest to measure: You can’t see air.
That’s why grow room ventilation is one of the toughest aspects of your setup to get right. That leaves you with two options:
- Buy a quality fan from a brand you actually trust (a difficult task).
- Buy way more fan than you actually need (an unnecessary expense).
I’ve tried both options. I’ve purchased the cheap Chinese models on Amazon and been let down by their power (are you surprised?). I’ve also bought inline fans with more airflow than I should ever need, essentially flushing money down the drain (or, in this case, blowing it out the window).
However, there’s one inline fan manufacturer I’ve come to trust because they make quality products, deliver amazing customer service, and don’t lie about their flowrates, sound output, or other specs: TerraBloom.
IGT’s Pick for Best 4-Inch Inline Fan
TerraBloom ECMF-100 4-Inch Inline Fan
TerraBloom’s 4-inch inline fan is rated up to 160 CFM of airflow while using just 18W. Its variable-speed EC motor can be adjusted from 0-100% power without additional hum or noise.
TerraBloom’s 2-year warranty and excellent customer service give you total assurance that you’re truly getting the best inline duct fan out there from a brand you can trust.
TerraBloom’s Inline Fan in Action
Alternatives to TerraBloom’s Duct Fans
TerraBloom’s inline fans and filters are my favorites and the ones I recommend to all indoor growers. The company simply makes great products and treats every customer like a new customer, but they aren’t the only equipment manufacturer out there. Here are two other duct fans, which can be used for grow rooms, HVAC exhaust, and other ventilation applications.
AC Infinity Cloudline T4
A great duct fan from another leading manufacturer.
VIVOSUN 4-Inch Inline Fan
Discount option for budget growers with fewer features and inferior performance (don’t believe their CFM stats).
Is a 4-Inch Inline Fan the Right Size for You?
Fans are essential for ventilation, and a fan’s ability to ventilate is determined by its airflow.
Airflow is measured in CFM (cubic feet per minute). In general, the larger the fan, the higher its CFM rating. However, that isn’t always the case.
Your inline duct fan needs to be powerful enough to recycle all of the air in your grow environment with fresh air at least once every three minutes—ideally, faster.
Because duct fans are measured in CFM (cubic feet per minute), it’s easy to calculate how much fan you need:
- Measure the volume of your growing tent or room. You can probably find this in the spec list of the product, you can measure the dimensions and use your third-grade math skills. For example, a 5′ x 5′ x 6′ grow tent has a volume of 150 cubic feet.
- Divide the volume by 3 to find the minimum CFM of your unit. In our example, a 5′ x 5′ x 6′ grow room requires a fan with at least 50 CFM (150 / 3).
Wait, 50 CFM? That’s it? It doesn’t seem like you need much fan power in this example.
Pump the breaks. We aren’t done yet.
Pro Tip: Calculate your CFM needs
That number is the actual minimum flowrate you need assuming a perfectly efficient system. Few systems are perfectly efficient. Chances are you still have to adjust for other aspects of your grow environment:
- For HID grow lights, add 50% for non-cooled lights and 20% for cooled lights
- For inline carbon filters, add 60%
- For silencers, add 20%
- For CO2 enrichment, add 5%
- For hot, drier climates (think California), add 25%
- For hot, humid climates (think Florida), add 40%
Check out TerraBloom’s comparable 4-inch inline filter and forget about the fit.
TerraBloom 4-Inch Inline Filter
The best inline filter to pair with your 4-inch exhaust fan from the same trusted brand so you know they fit.
Looking for another inline duct fan?
If a 4-inch fan isn’t the right size for your air delivery needs and ventilation applications, add one of these sizes to your shopping cart.
Founder of IndoorGrowTech
I have my Masters in Horticulture and specialize in plant biology, specifically the impacts that changing environmental conditions have on photosynthesis, plant growth, and fruit production. I spent nearly 20 years working in research labs, and today I manage a commercial greenhouse in Northern California that focuses on sustainable agriculture.