Laminar airflow air purifiers have caught people’s attention based on the idea that laminar flow can make portable air purifiers better at preventing infection. The logic is that laminar flow prevents nearby air from being caught up with the clean air coming from the purifier. But can small purifiers produce laminar flow, and does it actually make a difference?
What is Laminar Airflow?
Laminar airflow is the smooth, steady movement of air. In laminar airflow, particles flow in parallel layers that have little or no mixing with surrounding air. Turbulent airflow is the opposite, with lots of choppiness and mixing.
One easy way to think about laminar flow is like water in a river. Laminar airflow is like a river that’s flowing smoothly downstream. Turbulent airflow is like a river with rapids, swirling water, and lots of splashes.
In everyday life, true laminar airflow is hard to achieve because the environment constantly disrupts airflow. Furniture, walls, fans, air conditioning, and people moving around all disrupt laminar flow.
That means even if the air coming out of a fan starts out laminar, it will often quickly become turbulent on its edges as it mixes with the surrounding air. The farther you move from the fan, the more turbulent the airflow becomes.
Where is Laminar Airflow Normally Used?
The idea of laminar flow makes a lot more sense in industries that use it. Organizations use laminar airflow in highly controlled environments like operating rooms, semiconductor manufacturing factories, and biotech labs. These industries use laminar airflow to keep any potential contaminants produced in the lab from mixing with the air in the room and causing problems. A laminar airflow system pushes those contaminants straight out of the room.
Imagine standing in a cleanroom that uses laminar airflow. Here, air flows vertically from large air purifiers (called “fan-filter units”) in the ceiling down to the vented panels or grilles on the floor. Because the air moves directly down and out, it stays smooth and unidirectional, minimizing any contamination. However, if the grilles in the floor were blocked, the air would start bouncing around, causing turbulence and allowing particles to mix with the room air.
The same thing would happen with water. Imagine a calm river flowing smoothly out to sea. This is laminar flow. Now, imagine that the river is blocked with no clear path. The water would begin swirling and mixing, creating turbulent flow.
We can use this analogy to look at how air purifiers perform and whether laminar airflow is important.
Is Laminar Airflow Important for Personal Air Purifiers?
Some people take this concept of laminar airflow and apply it to portable air purifiers. However, the function of portable air purifiers isn’t to achieve laminar airflow. Instead, the function is to maximize the percentage of clean air the person gets.
If we have the same amount of air coming from a laminar versus turbulent airflow, it is reasonable to guess that the laminar flow will give the nearby person more clean air. Laminar airflow may help the clean air travel farther from the air purifier.
However, laminar airflow is probably much less important than the amount of clean air coming from the purifier. In fact, it’s possible to have 100% clean air even with fully turbulent flow, as long as there’s enough clean air being pushed out of the purifier.
Tests of Laminar Flow in Air Purifiers
A citizen scientist tested for laminar airflow in our QT3 portable air purifier and two other purifiers claimed to have laminar airflow. The test results showed that all of the purifiers had somewhat turbulent airflow. You can contrast these results with a truly laminar flow in this video.
None of the air purifiers had truly laminar airflow. Instead, a more accurate way to describe all the ones tested would be “less-turbulent airflow.”
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Does the QT3 Portable Air Purifier Have Laminar Airflow?
The QT3 portable air purifier has grilles that ensure air moves horizontally uniformly as it leaves the purifier. However, like other portable purifiers, the airflow becomes turbulent as it mixes with the air in the room. Therefore, the QT3 has less turbulent airflow coming right out of the air purifier, the airflow becomes more turbulent as it moves farther through the room. However, achieving 100% laminar airflow is not practical or necessary for portable purifiers in this type of real-world environment.
This is the Most Important Metric for Portable Air Purifiers
The key aspect to consider when comparing and choosing a portable air purifier is the percentage of clean air at the desired distance from the purifier.
For portable air purifiers, the primary goal is to achieve a high percentage of clean air in the breathing zone (directly in front of the purifier, where the person is sitting and breathing). We can measure this by putting a particle counter at different distances from the front of the purifier. As we like to do at Smart Air, we put it to the test! We repeated the test setup of other portable air purifiers by placing QT3 on the floor.
The real question is: how well does the QT3 deliver clean air within a reasonable distance? We defined “reasonable distance” as 30 centimeters because that’s how close someone would put it on a desk. Of course, people sometimes put the QT3 closer or farther away.
At 30 cm, the QT3 provided 75% cleaner air. Some people calculate “exposure reduction” factors, which would be 4 in this case (1 / (1 – 0.75) = 4).
The data suggests that the closer you are to the QT3, the more clean air you will breathe. In our tests, keeping within an arm’s distance (64 cm) of the QT3 produced air that was 40% cleaner air than it would be without the QT3.
Even when the QT3 was 1.2 m away in our tests, it produced about 25-30% cleaner air.
Read more: Does the QT3 Portable Air Purifier Work?
Bottom Line: The Truth About Laminar Airflow in Air Purifiers: Myth or Reality?
No air purifier can achieve 100% laminar airflow at a practical distance. Airflow will turn turbulent in most real-world conditions. The percentage of clean air at particular distances already accounts for the effects of different types of airflow, making it a more useful metric than laminar airflow.
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