A filter is a device used to separate particles from a liquid or gas, for example in HVAC for graded environments a series of filters (Bag Filter, HEPA) are used to remove particulates and microbes from the air.
Filters are commonly used for sterilisation of services or product, for example a system that requires sterile nitrogen could use
In high criticality situations, double filtration is commonly used to:
- improve performance of the filtration
- Reduce risk of filter failure causing a batch/campaign write-off
Filters capture particulates through four main mechanisms:
- Impaction
- Interception
- Diffusion
- Electrostatic attraction - Only for charged particles
Filters typically define a MPPS value and what percentage of MPPS particulates are filtered.