C h a p t e r
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X R F t e c h n i q u e a p p l i e d t o t h e au t o m o b i l e
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C H A P T E R 4 . X R F T E C H N I Q U E A P P L I E D T O T H E AU T O M O B I L E I N D U S T RY
the aerosol levels inside their facilities on a more real time scope. This need is even greater if we consider that at any given time there are hundreds of workers inside the factory working in the production stations.
Aerosol exposure, as we will discuss in this chapter, can be hazardous to human be-ings both from short time to long time exposure. Elemental concentrations of suspended matter are key to determine its toxicity to human health and are legislated accordingly.
However, legislation is mostly based on short time exposure studies due to their abun-dance relative to their counterparts. This means that even if some element’s dose is legislated with a certain threshold, it is hard to say what happens to an individual that is exposed below this threshold for a full working day, five days a week, through several years. Currently, studies on long time exposure are scarce due to their own premise. The main goal of preventive measures must be to minimize aerosol exposure to well bellow the legislative thresholds.
Repeated exposure to suspended particles allows for consistent deposition on the hu-man respiratory tract (HRT). The deeper on the HRT these particles can get, the bigger the impact on the health of the individual. This deposition has been associated with chronic inflammatory responses which in turn has been correlated with both cardiovascular and respiratory diseases and conditions. Several autoimmune responses are connected with aerosol inhaling, being allergic reactions the most common one. Since, the HRT is an in-terface from the atmosphere into the human body, toxic substances that can be suspended onto other particles can cause poisoning (for example heavy metals).
As for the source apportionment of the aerosol, there are several pollutants inside the factory. One of the major contributors, and perhaps the most interesting to study, is soldering and welding fumes that suspend mostly metallic based particles into the factory atmosphere. There are several welding stations across the body shop production line with some being manual, others automated and also mixed stations. These will be at the center of our study given their known impact in the deterioration of the air quality in a factory environment [110][111]. There are also a lot of robots and automated machines inside the factory which may suspend particles of their own due to exhausts or machine wearing.
Another source can be identified in painting stations since they aerosolise enormous amounts of particles, however these are isolated from the main assembly line, and hence, not relevant for this analysis. On top of that, workers themselves contribute to the shifting composition of the air, breathing in oxygen and exhaling carbon oxides and water vapor acting as catalysts in new particle formation.
Ventilation is one of the key aspects for air quality maintenance. It is very impor-tant that all the aerosol particles are extracted in order to allow for new clean air to be available for breathing. On this front, the factory already possesses a lot of vents capable of extracting air. There are two types of vents: some for general factory air, that are evenly distributed across the buildings, and also vents in more polluting stations (such as welding stations) for more targeted extraction.
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4 . 1 . S C O P E A N D O B J E C T I V E S
Another relevant aspect is that even before the COVID-19 pandemic there were al-ready stations that required some kind of respiratory protection. This might be the best human protection against highly aerosolised environments. This usually comes in the form of filtered masks with stations being classified into three types: no need for mask, needs a strap on filtered mask, needs a higher grade filtered mask with its own air source.
Air quality is one ofVolkswagen Autoeuropa, lda.focuses and as such this project aims to build a prototype capable of measuring changes to factory air in real time. This device has the following prerequisites:
• self-sustained - has its own power source compatible with the standard power grid
• real time like measurements - it is capable of small acquisitions in time frame of minutes to one hour
• fully automated and independent - it needs to have its own processing units and to be capable of performing several automated tasks
• communications units - it needs to have the capability of measuring and communi-cating through a platform that’s independent of company’s infrastructures
• remotely operated - acquisitions and other operations can be launched remotely
• portable - a small enough device that can be transported and moved from station to station
• scalable - must be a blueprint that can be easily reproducible for the purpose of multi device analysis
• low-cost - the price point of the whole instrument must be below 500e
Our main analysis tool will be based on Energy Dispersive X-Ray Fluorescence (EDXRF) technique[112,113], which was discussed in section1.1. As we anticipate that our aerosol samples will have a major contribution from welding, it is expected that a lot of metallic light elements will be found. This technique has great sensitivity to these kind of ele-ments, hence being well suited for this study. Moreover, this is a very versatile technique which allows for cheap and fast quantification of samples with a low level of sample preparation[6]. These characteristics make it very viable to use on devices with spec-ifications as the determined above. This technique allows for both on-lineandoff-line measurements without significantly affecting its portability.
For size distribution assessment we have opted to use a mix between binocular micro-camera optical inspection and a scanning electron microscopy (SEM) analysis which will be performed off-line. These two methods will then allow us to get some extra informa-tion on the deposited filters particles. Shapes and sizes will then be observed and hence a profile of the deposited aerosol can then be construct.
C H A P T E R 4 . X R F T E C H N I Q U E A P P L I E D T O T H E AU T O M O B I L E I N D U S T RY
In the following sections we will give some complementary insight of the object of study of this work - aerosols (4.2). In chapter5we will describe design and development of the prototypes built in this project. In this chapter all the engineering decisions and hardware and software parts used will be discussed. In chapter6 we will present the experimental setups and results achieved with these prototypes as well as their analysis and discussion.