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What Is Not Measured Cannot Be Controlled: How Ecogate greenBOX Measures Air Velocity and Air Volume

The Importance of Measuring Ventilation Values

In industrial exhaust ventilation systems, the primary function is to remove dust, fumes, or mist from workstations through air suction. To ensure proper functionality, it's essential to achieve the desired design air velocity and air volume at each workstation. Moreover, to maintain safe operation, these systems must uphold minimum transport air velocities throughout the entire duct system, as mandated by the NFPA 660 standard. As the saying goes, "What is not measured cannot be controlled," which is why measuring air velocities is paramount.

It's important to note that systems regulating to constant pressure cannot maintain minimum transport air velocities. To learn more about this, check out our article: "Why Ecogate's greenBOX is the Top Choice for Industrial Ventilation in 2023"

Now, let's explore how the Ecogate greenBOX measures air velocities in the duct system, ensuring your facility maintains optimal ventilation performance.

Measuring Air Velocities and Air Volume at Gates

The Ecogate system measures air velocity and air volume at each gate, which is crucial for monitoring whether each workstation achieves its design ventilation values (air velocity and air volume). By defining which gates are connected to specific duct branches and their respective diameters, the system calculates the air volume for each branch based on the sum of the air volumes of all connected gates. It also determines the branch air velocity using the branch air volume and diameter.

Ecogate greenBOX user interface shows Pressure, Air Velocity, and Air Volume measured at gate, i.e. at drop to the workstation

System Level Air Velocity and Air Volume

The Ecogate system is using several options to measure air velocity and air volume because not all options are possible or practical in all types of the systems.

Note: some systems attempt to measure main duct air velocity by using pressure sensors. However, pressure can only be converted to air velocity if the resistance before the pressure sensor remains constant, which is not the case in systems with varying gate open/close positions.

To accommodate the diverse needs of various ventilation system types and setups, the Ecogate system offers multiple options for measuring air velocity and air volume. This flexibility ensures that the system can adapt to the unique constraints and requirements of each facility.

It's worth noting that some systems attempt to measure main duct air velocity using pressure sensors. This method however, has a significant limitation: pressure can only be accurately converted to air velocity if the resistance before the pressure sensor remains constant. In systems with varying gate open/close positions, this resistance fluctuates, rendering the pressure-based velocity measurement unreliable.

Main Duct Air Measurement options
Main Duct Air Measurement options

Recognizing this challenge, the Ecogate system provides three robust methods for measuring air velocity and air volume: External Air Velocity Sensor, Sum of Gate Air Volumes, and Fan Power, Fan Pressure, and Fan Efficiency. Let's explore each of these methods in more detail.

Method 1: External Air Velocity Sensor

For the most precise air velocity and volume measurements, Ecogate recommends using our "Averaging Air Velocity Sensor." This sensor is designed to read air velocity across the entire diameter of the duct system, ensuring accurate readings even when air velocities vary at different points within the duct.

Based on the pitot tube principle, the Averaging Air Velocity Sensor measures velocity and static pressures at intervals across the duct diameter. To maintain accuracy, this sensor must be installed in a clean air duct, typically located between the dust collector filter and fan inlet. While the air volume here matches that of the main duct, the air velocity must be recalculated for the main duct before the dust collector inlet, which is often slightly smaller than the outlet duct or the duct between the filter system and fan.

Although this method offers high precision, it may not be suitable for smaller systems where the fan is directly installed at the filter outlet or for older systems with fans installed in dirty air before the dust collector. In such cases, the Ecogate system provides two alternative methods to ensure accurate air velocity and volume measurements.

Method 2: Sum of Gates Air Volumes

The Ecogate system's ability to measure air volume at each gate provides another reliable method for determining system-level air velocity and volume. As Ecogate Smart Gates continuously measure and transmit air volume data to the greenBOX control unit, the system can calculate the total air volume by summing the air volumes of all gates. This method is particularly useful in installations where all drops are equipped with Ecogate gates, which is common in Ecogate installations.

Once the total system air volume is known, the main duct air velocity can be easily calculated using the main duct diameter. This approach offers a practical and accurate alternative to external air velocity sensors, leveraging the Ecogate system's built-in gate-level monitoring capabilities.

Method 3: By Fan Power, Fan Pressure, and Fan Efficiency

For situations where external air velocity sensors or the Sum of Gate Air Volumes method may not be feasible, the Ecogate system offers a third practical approach. This method involves using fan power (precisely measured by the Power Master VFD), fan total static pressure (measured by the fan sensor provided with each Power Master VFD), and fan efficiency to calculate air velocity and volume.

By reversing the formula used to calculate fan power, the Ecogate system can determine the air volume and velocity based on the available fan data. Since the manufacturer's efficiency value is based on ideal conditions (as defined by the AMCA standard measurement), the real-life installed efficiency is often up to 5% lower. To account for this difference, Ecogate allows users to calibrate the system by entering the air velocity measured across the duct diameter using the averaging function of the Fluke 922 meter. This enables the greenBOX software to calculate the actual installed fan efficiency, ensuring accurate measurements.

The main duct air velocity is displayed during setup, enabling precise system fine-tuning


Ecogate offers three practical methods for measuring air velocities and air volumes, each tailored to different installation types and system configurations. Whether you choose to use external air velocity sensors, the Sum of Gate Air Volumes method, or the Fan Power, Fan Pressure, and Fan Efficiency approach, Ecogate ensures accurate, real-time ventilation measurements. This capability is especially beneficial as factory setups evolve, allowing for easy adjustments based on real-time data.

With Ecogate, you can properly adjust system performance while viewing all drop air velocities, system air volume, and velocities in real-time on the greenBOX control unit or via remote access. To measure all the values displayed on the greenBOX screen would typically require several hours of hard work by a skilled technician, especially considering the difficulty of accessing all the measurement points in a real factory setting. After the initial measurement, you would need to make adjustments and repeat the process, which is simply impractical.

The speed and convenience of Ecogate's air velocity and air volume measurements become even more crucial when you consider that real factory ventilation systems often change on a monthly basis due to the addition, removal, or relocation of workstations. The biggest benefit of Ecogate systems is the ability to easily adjust system performance based on real-time measurements

The dashboard on one of the ventilations systems shows required air volume (darker brown color) and measured air volume (at brighter color and by numerical value)

Video Demo

Accessing the Gate Pressure, Air Velocity, and Air Volume Measurements in the greenBOX's user interface


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