AM dust filters

[Jason Lixfeld <jason () lixfeld ca>]

Hi,

I'm interested in knowing what sorts of material folks use to make after-market dust filters for their various devices 
which wouldn't normally have any.  This seems to almost be a necessity when these kinds of devices are deployed in 
environments that are overly dusty and dirty (it should also be implied that these environments are all in-doors and 
would have less than ideal airflow and climate control).

A material that is too dense will hider airflow and cause an immediate increase in inlet temperature, which would 
exacerbate a potentially threatening temperature situation in environments where the ambient temperature is already in 
the mid to high twenties and above (that's 77 - 86F+ for my American friends ;)).  A material that is not dense enough 
won't do a very good job at filtering.

Do folks just hack up HEPA filters or something?