Did you know that the physical size of Hospital HEPA filters and housings are typically much larger than standard HVAC pre-filters and frames?
This is due to the construction of HEPA filters and HEPA media, and the resulting static pressure to achieve the required airflow rates and air changes per hour within various Hospital areas as specified by AS 1668.2:2012.
The fine sieve like structure of HEPA filter media makes it challenging for air to pass through the filter, so to achieve airflow and face velocity requirements, the surface area of the filter must be vast.
Thus, HEPA filters are designed for maximum surface area – with metres of moisture resistant micro glass fibre media pleated into tiny accordion-like shapes. Every 1m2 of HEPA filter face area contains roughly 20m2 of filter media – which is a tremendous surface area to effectively capture and restrain contaminants as air flows through the filter.
Correct sizing and design of HEPA filters are important factors for the filters to handle the right airflow rates and to meet the required air changes per hour specified by AS 1668.2:2012.
When selecting HEPA filters, the designer considers the air flow requirements of the room, and based on available static pressure capabilities, the HEPA face area is selected from data tables on the Airepure product brochures for given HEPA types.
Designers should ensure that adequate physical space is allocated for HEPA filters and housings during the design phase, rather than the building phase. It can be inconvenient and costly to all concerned if space allocation is incorrect.
Test ports and access hatches should also be included during the design phase to allow for NATA testing services such as the verification of HEPA performance during commissioning and for annual HEPA integrity testing.
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