Two Stage Air Filter
A disposable air filter for an HVAC system, especially a re-circulating system, having a first filter layer for removing larger particles and dust, and a second filter layer for removing small particles, especially reprievable particles. An expanded metal screen between layers is disclosed as a second embodiment.
1 . A disposable air filter for an HVAC system comprising:
a) a first layer having a large particle cut-off;
b) a second filter layer having a high efficiency and a small particle cut-off; and
c) a frame holding the filters in fixed relationship and sized to fit into a duct flange in the HVAC system.
2 . A disposable air filter according to claim 1 wherein both of said first and second filter layers are electrostatically charged.
3 . A disposable air filter according to claim 1 having a MERV rating of 10 or higher.
4 . A disposable air filter according to claim 1 wherein said second filter layer is pleated.
5 . A disposable air filter according to claim 1 further comprising an expanded metal layer between said first and second filter layers.