Problem: Maintaining air quality is essential to meeting criteria for cleanroom standards, and air quality cannot be measured without also measuring the air flow within the cleanroom environment. Specialized tools are required to gather the readings that represent the air flow through the ventilation systems, as well as a solid understanding of those systems.

Solution: There are several types of ventilation system setups commonly used in cleanrooms — each of which are put in place to remove contaminants from the environment and help meet and maintain cleanroom standards. It is necessary to check the air flow of those ventilation systems periodically, as many factors can affect the movement of air over time, such as buildups in the ducts, leaks, aging and worn fans and pumps, etc. Here we identify the most common types of ventilation systems used in cleanrooms and the most appropriate instrumentation to monitor the airflow throughout those systems.

Laminar flow systems employ unidirectional air flow, wherein the air moves either laterally or top-to-bottom. In this system, it is necessary to check air flow at the supply vents and throughout the room itself. At the vents or fan filters, the volumetric flow is determined by multiplying the average or center air velocity (V) by the area of the vent or fan filter (A), or Q = V x A. To determine the total volumetric flow of the cleanroom, the value (Q) of each vent or fan filter is taken and averaged. That value is then compared against the specifications dictated by the appropriate cleanroom standard and it can then be determined if the cleanroom in question is within the acceptable tolerance. Kanomax anemometers automatically calculate the total volumetric flow as each new reading is taken from the vents and/or fan filters, saving time and minimizing room for error by decreasing steps and the need to manually record values between readings.

There are few different Kanomax instruments, in fact, that are useful in taking cleanroom air flow measurements. Either thermal (hot wire) or vane type anemometers are ideal for gathering readings from vents and fan filters, as the flow rate is typically quite low in cleanrooms (usually between 0.2 to 0.5 m/s) and they can attain accurate readings from minimal velocities. But Kanomax capture hoods, on the other hand, are critical for measuring air flow changes through diffusers and other large openings into the cleanroom as they can be set in place with the “slow-low” tripod stands and left to gather readings over a predetermined period. This will allow technicians to determine the consistency of the air flow and pinpoint when/if it becomes insufficient or otherwise impeded.

The second most common type of air flow ventilation system found in cleanrooms is the “non-laminar” or “turbulent airflow” system. It is designed to remove contaminants based on a certain number of air exchange rates per hour. To check this type of system, the air flow is measured at both the supply and return points and calculate the number of times the air was exchanged in each hour. Again, Kanomax anemometers and capture hoods greatly reduce the amount of manual calculations and noted readings that a technician will have be responsible for due to the intuitive software that pre-installed on the units.

For more information about this product, visit www.kanomax-usa.com.