The microbiological tests have been carried out according to the
count-reduction test (CRT) (VDMA, 2008). As test samples, B.
atrophaeus spores inoculated on aluminum strips were used. The
initial bacterial count was on average at 2.04*106 cfu (colony
forming units) per strip. After exposure to the sterilising gas, the
test strips have been stored in 10 ml Ringer's solution. Afterwards,
the spores were stripped off the aluminium strip in an ultrasonic
bath and plated on nutrient agar. To ensure that a countable
number of bacterial colonies (