Truth about airflow ratings of air circulation fans!

So you are trying to find air circulation fans for your grow operation and you are finding that there are all sorts of numbers that show the performance of different units. So what should you do with this information? You should ignore it! 

First a bit of explanation

The performance numbers that you are seeing are the volume of air moved by the air circulation fan during a certain period of time. The most common units applied are CFM which is cubic feet per minute. You might see cubic meters per second which is the metric system measurement.

Why should you ignore the ratings?Enter heading here...

Because there is currently no single standard for measurement in use which makes the ratings impossible to compare! This isn't just an opinion, we have proved it time and again in the laboratory. And this isn't limited to equipment found in North America, the same issue was found by an agricultural scientist in Japan some years ago*.

Another reason that you should ignore the ratings; they don't tell you what you want to know! What you are trying to achieve is a certain airflow across your entire crop not a specific airflow. It is quite possible that even if the airflow of two units is exactly the same the airflow pattern is quite different.

Airflow of Circulation Fans

These differences are going to make a big difference in how you select and apply the fans.

So what should you do?How do you select fans?


First, when trying to compare the various performances use the size and power of the units as a guide rather than published air flow ratings.You can use the horsepower rating or even better the power consumed by the fans (usually in watts).This will give you a better comparison of the overall performance of various units.

Second, seek out units that provide velocity profiles of the performance.This will allow you to create a pattern of airflow that best meets your needs.

*"Evaluation Indicator for Greenhouse Air Circulator Performances" Takeshi Kuroyanagi Engineering in Agriculture, Environment, and Food 2013



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