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Cage Filter Test Unit
What is the Cage Filter Test Unit ?
The cages used in the IVC (individually ventilated cage) racks have capsule HEPA filters fitted into the rear part of the lid. These filters clean the air supply into the cage and also clean the air exhausting out of the cage. Over time, these filters (particularly the exhaust filter) soil and become partially blocked. This can reduce the ventilation rate through the cage and also affect the cage pressure. It is important therefore to occasionally test the capsule filters for blockage (and leakage).
There are two types of Filter Test Unit (FTU) available. One tests the filters in-situ mounted on the cage and the other one tests a single filter. This section describes the first type.
The Filter Test Unit has only one application and that is to check the status of the cage capsule filters.
How does it work?
There is a small fan located inside the FTU. When the cage is offered into the FTU, a micro switch closes causing the fan to run, drawing air through the cage filters. A sensor inside the FTU measures the pressure drop across the filters and a circuit board processes the result. If the pressure drop is outside preset limits a red LED will indicate filters blocked or leaking. If the pressure drop is within limits, a green LED will indicate filters serviceable.
The degree of blockage of filter is reprogrammable using DIP switches inside the FTU, and the FTU may be calibrated to a new filter before testing as filters can vary from batch to batch.
The advantage of using the FTU is that the IVC will run at optimum conditions if the filters are within design limits. This provides the best possible work and operator protection. Also, disposing of filters only when outside their operational life, is likely to bring cost savings by extracting the maximum life possible.