Image Number 4 for United States Patent #4663293.
In a device for testing air for microorganism content with a rapidly rotating impeller inside a cylinder that has a backing sheet coated with culture medium against its inside surface, microorganisms that vary more extensively in size can be detected with almost equal effectiveness, the throughput of air can easily be determined, and the precipitation effect can be precisely tested because the backing sheet rotates along with the impeller, the blades of the propeller are at a low angle to the plane it rotates in, the air enters at a location that is separate from the location at which it leaves, through inlets from above and down and out through outlets, and the inner surface of the rotor below the impeller chamber is in the form of a channeling cylinder.
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