Fiberglass and Polyester Disposables

Although most filters are considered disposable, no other filter style is so easily discarded.  The disposable style filters are characterized by a chipboard cardboard frame with either course fiber fiberglass or polyester media.  Fiberglass media is generally a MERV 1-4 and Polyester media is a MERV 4.  Both media types are less than 20% efficient and offer little value in improving Indoor Air Quality.  They are used in low velocity applications that require minimum resistance across the filter.  The recommended change out period is between 30 days and 3 months. 

Manufacturer variations include:

• Pinched Frame- Provides width necessary for track but reduces media to less than ¼” thick.  Available in ½”, 1”, and 2” thicknesses.
• Scrim Backing- On downstream side provides retention of media in frame and prevents media oscillation which causes premature off loading.  This feature does not add to the structural integrity of the frame and typically bows with use.
• Metal Grid- Available on downstream and upstream sides, this feature adds to the structural integrity of the frame as well as prevents media oscillation.  Metal retaining grid also prevents bowing on very long run filter tracks.

Positives:

• Very Low Cost
• Custom Sizes Available
• Very Low Resistance

Negatives:

• No value for improved Indoor Air Quality
• Will bow and collapse with heavy dust loads
• Off loading of captured dirt when full