The sterilization characteristics of active species generated by an atmospheric dielectric barrier discharge plasma using air and oxygen at the inner surface of silicone tubing were investigated. A dielectric barrier discharge torch plasma device was installed at one end of the tube and generated long-lived active species that flowed into the tube. A strip-type biological indicator with a 105-cell bacterial spore was placed at the opposite end of the 60 cm tube. Sterilization was completed within 30 min by active particles generated from the air plasma. The main factors contributing to the sterilization by air plasma were HNO3 and N2O5. When organic materials (keratin, aspartic acid, and dipicolinic acid) reflecting components of the bacterial spore, were treated by the sterilization procedure there was little effect on dipicolinic acid. Keratin was oxidized by ozone and NOx generated from the oxygen and air plasmas, respectively. Aspartic acid underwent little change in composition from ozone generated from the oxygen plasma, whereas nitro (NO2), nitroso (NO), and aldehyde (CHO) groups were formed from ozone and NOx generated from the air plasma.

The sterilization characteristics of the inner surface of silicon tube were investigated using active species generated by atmospheric dielectric barrier discharge (DBD) plasma using air and oxygen gas. A DBD torch-type device installed at one end of the tube and generated long-lifetime active species flowing into the tube. The strip-type BI (Biological indicator) with 105 spore-forming bacteria placed at the position opposite to the DBD device in a 60 cm tube was sterilized within 30 min by active particles generated from air plasma. Major factors for the sterilization using air plasma were HNO3 and N2O5. When the organic materials (keratin, aspartic acid and dipicolinic acid) comprising spores were treated same as sterilization, the treatment hardly changed the composition of dipicolinic acid. Keratin was oxidized by ozone and NOx generated from oxygen plasma and air plasma. The result of aspartic acid showed little change in composition by ozone generated from oxygen plasma, whereas nitro (NO2), nitroso (NO) and aldehyde (CHO) groups were formed by ozone and NOx generated from air plasma.