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ABOUT BAG SIZE:
AFC has introduced the reasonable and logical method for
denoting the size of bags. In the past bags were assigned
sizes based upon the maximal volume the bag could hold. This
was a bad system for the following reasons:
1. That volume is uncertain. All plastic bags will stretch to
some extent, depending on temperature, pressure, and relaxation
time. Accordingly, the assigned volumes are completely
arbitrary.
2. That "maximal" volume is virtually never used. Bags are
seldom filled to maximal volume, they are generally used for
purposes other than to carry a large volume.
3. The "maximal" volume gives little clue to the actual size of the
bag. This makes it difficult for a user to select a bag for a
given application.
THE AFC BAG SIZE STANDARD: The AFC standard size criteria is
the number of milliliters of water that the bag will hold when the
bag is restrained between two rigid plates spaced apart 1.0
centimeter when the water is permitted to fill the bag without head
pressure for one minute at room temperature. We use that volume as
the second portion of our catalog number. For reference
purposes we also provide the maximum fill volume of water the bag
will hold when suspended by its ports and filled to maximal
extension after one minute with no head pressure. We also
provide the surface area of the bag, both sides, for purposes of
calculating gas exchange.
WHY ONE CENTIMETER: The selection of one centimeter
thickness was based on research which indicated that human
lymphocytes would expand at a maximal rate when the media fill was
one centimeter thick. Greater thickness provided no greater
expansion and is accordingly a waste of media. Lesser fill thickness
resulted in lower expansion rates and is accordingly a waste of
time.
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Standard Bags
