| http://www.w3.org/ns/prov#value | - U.S. Pat. Nos. 4,874,659 and 4,178,157 both teach high efficiency particulate air filters capable of filtering out 99.97% of 0.3 ??m particulates in air flowing at 5 cm/sec, characterized by lower pressure drop in a range of 5-10 mm H2O. These filters are made of nonwoven web (U.S. Pat. No. 4,874,659) or sliced films (U.S. Pat. No. 4,178,157) made of polyolefines, such as polyethylene or polypropy
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