The Study On Key Issues Of Self-Inhalation Filter Type Resipratory Protective Technology

Recently, more than sixty eight percents of cities in China had been attacked by particulate contaminant in munituple environment. For against such severe ambient particulate pollution and to prevent PM into respiratory system, donning self-inhalation filter type respirator may be a typical and economical protective measure. However, commercial N95 cup-type half-mask respirator and medical surgery folding respirator and gauze flat respiraor, while donned, maybe perform worse than expected. This study aims at key issues of self-inhalation filter type respiratory protective technology and demonstrates the original works with their methodologies and conclusions as the following.Firstly, the study contrasts the surrent performance requirements for testing simple respirator oversea and in China. The differences between those standards such as 84 CFR Part 84 (NIOSH) and EN149:2001 (EU) and requirements in China, show that those certified commercial self-inhalation filter type respirators, which are,N95 respirator and medical surgery respiator and gauze respirator, may perform unexpectedly firstly because of the undevelopment of certification index for performance testing. The contrasted results propose the references for developing new performance indexes applicable to China.Secondly, one of the widely recognized methodologies for testing respirator media is using TSI 8130 as test equipment and NaCL or DOP as test challenges. Basing on the analysis of TSI 8130, this study constructs two new systems for testing the protective performance of respirator against ambient aerosols. The results of analysis show that the performance of gauze respirators were so bad that many layers of gauze respirator may not protect persons from infection. On the other hand, high porosity electret fiber media with high efficient and low resistance against ambient aerosols may be the relatively optimal filter media for respirators. Additionally, the flat-type of respirator meant that more surfaces of filter media could be sealed to subjects’ skin and the fit factor could be increased. So, flat-type may be the optimal profile for respirators.Fourthly, this study structures a new probability prediction model for fit performance of respirator donned on a group of subjects basing on beta distribution and Poisson distribution. The . new prediction model uses a small number of parameters to predict the probability of the mass quantity of particulate contaminants being higher than occupational exposure limit. The results from the prediction model show that subjects donning a respirator for a long time may inhale hazardous dose of particulate contaminants in a great probability, which is 44% for three subjects. Furthermore, three values, which are h-value,α-error andβ-error, are used to structure fit performance and test evaluation model to assess the fit performance of respirator and the accuracy of fit test methodology. The results from the evaluation model show that h-value affects the probability of assigned inadequate fit respirator more thanβ-error. Otherwise,α-error affects the test methodology accuracy more significant than other two values. Among h-value andβ-error, the former impacts the test methodology accuracy more than the latter. As a conclusion, NIOSH’s standards without considering the fit character of respirator may be unreasonable and will result in complication of respirator test program.Fifthly, the pressure and velocity in the chamber between the respirator and the face in inhaling period have been simulated by CFD methodology. The pressure and velocity field with half-circle or gap leakage and without leakage are analyzed in contrast. The results illustrate that gap leakage affects the field more significant that half-circle leakage. Moreover, cheek leakage may markedly decrease the stivy feeling of respirator wearers. Those conclusions propose that the optimal respirators be designed in accordance with fit test panel and equipped with elasticated materials on their edge, and improved their top and bottom structure. At last, the top half-chamber of respirator should be elaborately improved in order to reduce the leakages.Lastly, this study compares data of facial anthropometric dimensions for 461 Chinese subjects and for other race/ethnic groups, such as American and Korean and Australian. A new respirator fit test panel must be structured for Chinese because the differences in the facial size between those races are so significant that the current respirator fit test panels are not be applicable to Chinese. The data from 1988 Chinese adult facial size survey are utilized for evaluating the applicability of new respirator fit test panel for Chinese. The results show that the new respirator fit test panel proposed by this study can accommodate the most of data from the facial anthropometric survey in the study and can be applicable to Chinese for respirator designing and fit testing.Basing on the conclusions, a new type respirators had been designed and been brought about industrialization, which shown a good social significance. Finally, this study also proposed disadvantages of the research and the trend for their development.This study used ambient aerosols as the challenge and developed the new self-inhalation filter type respiratory protective technology, which not only applicable to Chinese but also to other races. As a whole, the results of this research show a good scientific significance and technological innovation.