The NAFA Guide to Air Filtration (1993) points out that, "The use of HEPA filters to remove bacteria from the air stream has been well documented. One report gave the result of tests on four different HEPA filters, which had been purchased on the open market. In this series of tests ... bacillus subtilis spores ... were used as a challenge."
Average penetration was found to be 0.00069% and average efficiency of 99.9993% resulted.
