Description
In rooms with special requirements for air cleanliness, for example, in highly aseptic operating theaters in medical institutions, or in clean Class A zones in pharmaceutical production, air supply to the critical zone should be carried out using laminar, i.e., unidirectional air flow that does not have significant turbulence, since the turbulent flow is able to capture and introduce pollution into the critical zone from the surrounding space.
To create a unidirectional air flow, special air distributors or large area laminators should be used, leveling the speed of the air entering through the ventilation. Around the perimeter of the laminar flow should be limited to lamellae or curtains, to prevent premature flow of the flow.
In the ideal case, when designing a room with a laminar flow, the exhaust air intake grilles should have a slightly larger area than the required laminar flow area, and should be located exactly opposite to the direction of the air. In practice, unfortunately, this situation is extremely rare.
How is laminarity and unidirectional air velocity measured?
Measurements are carried out using a hot-wire anemometer on the grid, which breaks the cross-section of the supposed laminar flow into identical squares with a side of not more than 0.5 m.
The measured flow rate at all points should not differ by more than 10%.
If necessary, visually assess the uniformity of flow can be used generator of aerosol particles for the visualization of air flow.
Regulatory documents also regulate the measurement of the cleanliness class in an area with unidirectional air flow, since the cleanliness class in the laminar zone is usually higher than in the rest of the room.
Test results in the laminar flow zone
The test report on clean rooms includes information on the presence of a unidirectional (laminar) flow zone in the room, measurements of aerosol particle concentration, cleanliness class of the room, unidirectional flow velocity and conclusions on the compliance of the laminar flow in a clean room with the requirements of regulatory documents.
