HEPA is short for "High Efficiency Particulate Arrestance". A HEPA filter bag traps a large amount of tiny particles that otherwise would pass through the vacuum machine simply return into the air.
HEPA filters fall into different categories depending on their efficiency. HEPA-10 traps 85% particles greater than 0.5 microns (µm) in diameter, HEPA-11 traps 95% and HEPA-12, 99.5%. Reducing or eliminating these particles will make your working environment a cleaner and safer place. In addition, these filter bags reduce or virtually eliminate particles reaching and clogging your machine’s main filter. The main filter lasts far longer thus saving you money in the long term.
These Numatic Hepa-Flo Dust Bags (NVM-3BH or 604017) offer 99% filtration when used with a Tritex or a Permatex filter and 99.9% when used with a Microtex filter. They have a 23 litre capacity and fit any of the Numatic range of vacuum cleaners that have a 570 or 500 sized drum, for example, WV 570, NVQ 570 HZQ 570.