Nick,

From what I understand from their website, the Envirosept uses a power
supply and media, therefore produces o-zone as well high resistance
media. The electrostatic filters typically used arrestance test for
efficiency, which has a large particle size dust for testing.

The media filters typically use dust spot test as opposed to arrestance
test used by electrostatic filters. A 95% arrestance rating on an
electrostatic filter is about the same as a 15 to 20% atmospheric dust
spot test. The tests are completely different, therefore no direct
co-relation.

Electrostatic filters don't work well below about 300 Feet per minute
air velocity, because they don't develope a charge below that air
speed. Therefore their high resistance to air flow is their own enemy.
If you oversize electrostatic filters to reduce resistance to air
flow, the velocity drops below the 300 FPM threshold and they loose
effectiveness.

The combination filters like Envirosept and Dynamic are the worst of
both worlfs. They have media which has high resistance to air flow
needs and replaced periodically $$$, and they produce ozone.
Nick, you should get a flow hood and a differential pressure gauge and
test the results before you recommend them to anyone. The saving grace
of the Envirosept is it seems to be a better than average filter, if
you have a powerful enough blower to overcome their high resistance to
air flow. As an option, put two filter grilles side by side, due to
the fan laws, since the velocity is 1/2, the pressure drop will be only
1/4 (the square of the change). Then the Envirosept becomes a more
interesting concept.

Just remember, if you use a high resistance/efficiency filter, your air
will be cleaner, but with reduced air flow your AC may not work well
and your efficiency will be reduced. (Unless you have a high powered
blower or oversized filter.)

Nick, half of the systems that I measure have air flow of 200 CFM/ ton
instead of the 400 CFM/ton they should have. Hence my dislike of high
efficiency/high resistance filters that reduce air flow another 10%
to20%.

Stretch