Air filters and extraction and exhaust systems should be designed and installed in such a manner as to enable their regular inspection and maintenance. To achieve optimum technical and hygienic operation, one should preferably have the inspection preformed by either internal or independent tradespersons. If you arrange for your own maintenance and inspection, then observe the EN 13779. VDI 6022-2 (2006) and VDI 3802(2002) standards.
The following are vital points for attention:
- The first filter stage should be installed as close as possible to the air intake or mixing chamber. In the event of an extremely high particulate matter load, an additional extra filter stage should be fitted in front of the outdoor air inlet.
- The second filter stage is the final element of the air treatment process. A second filter stage should always be installed if V-belt driven fans are used.
- The filter section should be readily accessible for visual inspections and the replacement of filter elements. Interior lighting should be fitted in lengths of 1.3 m and upwards, while dual access should be provided (in front of and behind the filter) in lengths upwards of 1.6 m. • Filter elements should be installed and replaced from the dirty air side.
- An airtight seal is essential, while the EN 1886 standard should be observed. Use filter frames with closed cell seals only.
- The airflow in filters should be constant, with a view to avoiding surges and contraflow.
- Bag filters should always be installed with the bag in a vertical position, to avoid contamination and saturation of the floor of the system.
- The system should be fitted with an indicator pressure differential manometer – not a liquid manometer therefore – and an operating hours counter.
- Fit measures to check the relative humidity, with a view to avoiding saturation and microbial growth. In the second stage also, relative humidity should remain < 90%.
- The same class of filter should be used for thermal wheels and filters in the return air section as those fitted in the intake air section. • The terminal resistance of the filter section should be determined on the basis of energy considerations (LCC and LCA) and the available output of the fan.
- The exterior of each filter section should clearly bear the following data:
– Airflow volume of the system (not that of the filters)
– the number of filters
– the filter class
– the filter dimensions
– the recommended terminal resistance of the filter system (not that of the filters)