Atmospheric pollutant monitoring constitutes a primordial activity in public policies concerning air quality. In São Paulo State, Brazil, the São Paulo State Environment Company (CETESB) maintains an automatic network which continuously monitors CO, SO(2), NO(x), O(3), and particulate matter concentrations in the air. The monitoring process accuracy is a fundamental condition for the actions to be taken by CETESB. As one of the support systems, a preventive maintenance program for the different analyzers used is part of the data quality strategy. Knowledge of the behavior of analyzer failure times could help optimize the program. To achieve this goal, the failure times of an ozone analyzer-considered a repairable system-were modeled by means of the nonhomogeneous Poisson process. The rate of occurrence of failures (ROCOF) was estimated for the intervals 0-70,800 h and 0-88,320 h, in which six and seven failures were observed, respectively. The results showed that the ROCOF estimate is influenced by the choice of the observation period, t(0) = 70,800 h and t(7) = 88,320 h in the cases analyzed. Identification of preventive maintenance actions, mainly when parts replacement occurs in the last interval of observation, is highlighted, justifying the alteration in the behavior of the inter-arrival times. The performance of a follow-up on each analyzer is recommended in order to record the impact of the performed preventive maintenance program on the enhancement of its useful life.
Due to the current growth of the Brazilian population income and energy consumption and an increase in the population density in urban areas, air quality in the crowded Brazilian cities is being questioned. In searching for a solution we analyzed both the Brazilian and Regional (São Paulo state) public policies of air quality that have been issued since 1981 by confronting them to the air quality official indexes. Following the growth of the national vehicle fleet, 48.8 million in 2012 from 9.3 million in 1980, the total carbon dioxide emissions tripled. At regional level, PM 2.5 measurements have been carried out systematically since 1999 in the Metropolitan Region of São Paulo city, the largest Brazilian city, with 19.7 million inhabitants, and more than 7 million vehicles powered mainly by fossil fuels. Although the numbers are still above the state standard to be reached (10µg.m -3), there was a decrease on the annual average in 2008-2015 compared with 2001-2007. This was partially due to the limits established for new vehicles by federal programs. The analysis indicated that the reduction of air pollutants emission will be more easily achieved based on strategies that combine policies supported by current laws, government and private sector agreements and the community engagement.
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