In article ,
"Mary Fisher" writes:

Q: what does HEPA mean?

High Efficiency Particulate Air [filter].

Years ago, they were used on the non-sealed disk drives we
used to use, which relied on positive air pressure through
HEPA filters to keep dust out. The HEPA filters had to be
changed every 6 months, and they were treated as a low level
biohazard because they trapped bacteria, and hence used ones
had a rather high concentration of bacteria inside them.

Like I said in an earlier post, I would not have bought that
feature except it was very much cheaper by virtue of a special
offer. I'm very much a believer in the modern obsession with
hygine being responsible for increase in various diseases, and
that the immune system needs to be exposed to a wide variety
of things to keep it working properly.

The only dirt which seems to have got trapped in mine is that
generated in the vacuum cleaner itself after the cyclone and
washable filter, i.e. dust from the motor brushes, which
considering how much it's been used and how little there was,
was really quite insignificant. (Actually, the HEPA filter
is designed to filter out dust far too small to see, so it
might be that it is being more effective than is visible by
eye.)

--
Andrew Gabriel