Study On The On-line Monitoring Of Gaseous Chlorine Dioxide Manufactured By Gas-solid Reaction And The Disinfection Of Slender Tube

The event of Anthrax spore contamination occurring in the United States postal system after "9*11 attacks" shows that biological terrorist attacks have become a real threat. For the SARS virus engulfing the entire world in 2003, the Influenza A(H1N1) virus outbreak in 2009, as well as the Ebola disease attacking the West African in 2014, it is reputed that the emerging and emergency infectious diseases pose a severe challenge to the public health security system. In responding to biological attacks and infectious diseases, in addition to isolation protection, the thorough decontamination of the bio-polluted objects such as buildings, cabins, equipment, and instruments is an imperative means, which can effectively block the dissemination of pathogenic microorganisms through air and objects. Spraying, wiping and other traditional disinfection technology can’t make a thorough disinfection on gaps, the bottom of device, filters and other porous objects or complex surfaces. Considering gas disinfectant has good characteristics of penetration and diffusion, gas fumigation is the most effective way to disinfect a space and the surface of objects in a space. Formaldehyde fumigation had ever widely used in space disinfection at home and abroad. Although formaldehyde has been eliminated in US and other countries because it was determined as a carcinogen by the World Health Organization, it is still widely used in China due to the lack of new technology.Gaseous chlorine dioxide (CD) is a sterilant widely recognized in the world, which has broad spectrum, high efficiency, safety and other features. Except for the disinfection of drinking water, and the preservation of food, it also used for the disinfection or sterilization of production facility, laboratory equipment, indoor environment, and indoor object surface. However, the research of gaseous CD in China has not yet made a real breakthrough in disinfection technology, and still limited in water disinfection and fruit preservation. Meanwhile, few achievements are made in the research of the disinfection of space and the surface of objects in spaces. Moreover, the research in the field of medical apparatus and instruments using gaseous CD is blank. The main reason is that some key technologies of space disinfection of gaseous CD have not been mastered, such as simple, quantitative and controllable pure gaseous CD generation technology, gaseous CD concentration on-line monitoring technology, and gaseous CD security applying technology. In this paper, some key technologies of gaseous CD disinfection were studied to provide technical support for the research of the disinfection technology of gaseous CD, expand the application of the excellent disinfectant of gaseous CD, as well as solve the practical demands of national biological safety and epidemic prevention.First of all, this paper carried out a research on the gaseous CD concentration on-line monitoring technology. According to the feature that gaseous CD has a strong spectral absorption from the UV to blue light, this paper studied the spectrum absorptive concentration sensor of gaseous CD. Based on the theoretical analysis, one type of simplified single wavelength dual optical path was designed. A LED with a center wavelength of 405nm was selected as light source in consideration of the features of gaseous CD in photolysis reaction. The control system of the sensor take ARM as the core, coupled with CPLD, and contained the LED drive circuit which can be sinusoid modulated, as well as the signal processing circuits with photoelectric conversion preamplifier, band-pass filter, and analog lock-in amplifier. To avoid a wide variety of reagents and the complex steps in using iodometry, this paper designed a convenient method to calibrate the standard curve of the concentration sensor of gaseous CD, in which a handheld CD detector with DPD theory was used to test the CD concentration of CD solution sampled by a precision syringe. This paper also tested the accuracy and consistency of the concentration sensor.Then, for some important application scenarios with the disinfection need of long and narrow tubes, such as the sampling pipe inside the biological detection equipment which might be contaminated by biological warfare agent, the endoscope and vitro ventilator which might infected by superbugs, this paper studied the disinfection efficacy of gaseous CD on the long and narrow lumen. To disinfect the lumen effectively using gaseous CD, an active circulation mode was innovatively designed. Meanwhile, one type of testing device composed of polytetrafluoroethylene (PTFE) tubes and bacterial carrier containers in the middle and ends was designed. PTFE bacterial carriers inoculated with Bacillus atrophaeus spores with or without organic burden were used to evaluate the sporicidal activity of gaseous CD under various conditions of exposure dosage, relative humidity (RH) and flow rate. And also, the RH distribution along the lumen was tested to explain the possible reasons of the differences of disinfection efficacy in different positions of the tube.Meanwhile, in view of the narrow gaps in practical disinfection application, such as incomplete sealed enclosure, and the lifting clamp device of a duodenoscope, this paper carried out the study on the sporicidal activity of gaseous CD on the stainless steel surface in a narrow gap. Various dimensions of the gap based a type of narrow gap experiment device were investigated.Finally, a pilot study on using gaseous CD for disinfection of gastrointestinal (GI) endoscopes was carried out. According to the results that the gaseous CD can kill the B. atrophaeus spores with high efficiency in the slender tube and narrow gap, it is reputed that the gaseous CD can be used in the disinfection of GI endoscopes. An experimental prototype of gaseous CD disinfector for GI endoscopes was developed based on the systematically studies on the gaseous CD generation using gas-solid method, safety handling technology of gaseous CD and chlorine gas, fast and stable steam humidifier special designed for negative pressure chamber, and gaseous CD absorber. An autoptic disinfecting test on real GI endoscopes after clinical use was performed using the experimental prototype in accordance with the designed operation procedure in view of the features of the CD disinfector.In summary, through the research in this paper, on the one hand, the preparation of the concentration sensor of gaseous CD provides a key technical support for the disinfection technology of gaseous CD in China; on the other hand, the research of the disinfection efficacy of gaseous CD on slender lumen and narrow gap, provides the technology and data references for the application of gaseous CD in the disinfection of space and the surface of objects in spaces; what’s more, the research of using gaseous CD for high-level disinfection of GI endoscopes, not only provides a lower cost and higher efficiency disinfection technique for digestive endoscopy department, but also further expands the application fields of gaseous CD.