Monitoring air pollution in industrial environment with wireless interface.

Machedon-Pisu, Mihai ; Nedelcu, Adrian ; Alexandru, Marian 等

1. INTRODUCTION

The analysis of the air particles within industrial buildings is necessary for medium protection: keeping the environmental pollution as low as possible, for improving workers' health: increasing the life expectancy and avoiding pulmonary diseases, and also for economic reasons: preventing the damage of the instruments and materials and also reducing the excessive use of raw materials. The limits imposed for the dust and resprirable particles in the atmosphere represent the starting point for evaluating the actual results of our monitoring application in industrial environment. Most harmful for health are the microdust particles with a 2.5 [micro]m diameter (PM 2.5) and less harmful, but also to be considered, are the respirable particles with a 10 um diameter (PM 10) (Ott et al., 2007). For the former, the European Parliament has established a limit of 25[micro]g/[m.sup.3], starting with the year 2010, and for the year 2020 this limit could reach a value of 20[micro]g/[m.sup.3]. For measuring the air concentration, the authors have used a real-time dust monitor. The results are highlighted in the following sections.

2. ANALYSIS WITH THE DUST MONITOR

2.1 Principle of the Dust Monitor

The dust monitor used is capable of estimating the concentration of the suspended particle matter. The variations in dust concentration are presented graphically on the instrument in real-time. Some of the features of this instrument are particularly suited for applications such as monitoring air pollution:

* The ability to measure from 1[micro]g/[m.sup.3] to 2.5 g/[m.sup.3].

* Measurement with logger in 15,700 points.

* The possibility to measure T.S.P., PM 2.5, PM 10 plus other respirable measurements.

* Remote control operation with PC.

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In order to measure the particulate concentration, the dust monitor uses a near forward light scattering technique (Fig. 1). Infrared light of 880nm wavelength is projected through the sensing volume where contact with particles causes the light to scatter (Fig. 2). The amount of scatter is proportional to the mass concentration and is measured by the photo-detector.

By using a narrow angle of scatter (12-20[degrees]) the majority of scattered light is in the diffracted and refracted components, which minimises the uncertainty associated with particle colour, shape and refractive index.

2.2 Adapters for the Dust Monitor

There are three different gravimetric adapters which are available with the dust monitor, and depending on the wanted measurement, these are:

* T.S.P.--all the particle samples are managed in real-time and deposited on a standard filter.

* Cyclone--only some respirable particles (with a 4 [micro]m diameter) get through the probe and are deposited on the filter.

* With P.U.F. (polyurethane foam)--the filters with P.U.F. can be selected for a standard size such as PM 2.5 for microdust particles with a 2.5 [micro]m diameter, PM 10 for respirable particles with 10 [micro]m or for respirable particles with 4 [micro]m (such as cyclone).

3. MEASUREMENTS

The concentration of the respirable and dust particles found in a hostile environment, such as a brickyard quarry, can be measured in real time. The four types of analysis possible with the dust monitor are T.S.P., cyclone, PM 2.5 and PM10. The results of the measurements performed in the industrial environment are presented in Figures 3 and 4. The measurements are evaluated for three zones inside a quarry.

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As can be seen in Figure 3, the PM 2.5 and PM 10 analyses reveal some interesting results when compared to the admissible levels for PM 2.5 (0.020 - 0.025mg/[m.sup.3]) and for PM 10 (0.05 mg/[m.sup.3]).

Figure 4 identifies the hot spots where those levels are exceeded. The distribution of particulate matter fluctuates depending on the zone where measurements are taken. Thus, placing dust monitors within the hot spots would seem as appropriate. Such a network where data is gathered from nodes active at that time (should be near the hot spots) is similar to an ad-hoc network (Shorey et al., 2006).

4. WIRELESS INTERFACE

The dust monitor sends data through a serial port. The software for the wireless interface is based on LabVIEW. The program we run provides a graphical representation of the bytes sent through the serial port to a transmitting device (Figure 5). This device is connected to a network from where its data can be accessed, using shared variables. Data is sent from the monitor to a device that has a serial port and a wireless transmitter (Lantronix's Wi-Port).

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Data is transmitted via the ad-hoc wireless network to a mobile device (a PDA client) or to a fixed location (a server) (Figure 6).

The wireless interface we present is based on an ad-hoc network with Wi-Fi (Fig. 6 a.). Another solution for the wireless interface could be the WSN (wireless sensor network) approach (Fig. 6 b.). Although there is less power consumption at the transmitters' side for WSN, the conversion from some wireless technology to Wi-Fi makes this approach unpractical. The PDA device represents the client side of the network, at which measurements are visualized in real time with LabVIEW. The measured data can also be stored on the server.

5. CONCLUSION

The measurements with the dust monitor in the quarry have shown that there are certain points where the admissible limits for PM 2.5 and PM 10 are exceeded. Monitoring these hot spots inside a hostile environment is possible with a wireless interface. The solution presented is based on a Wi-Fi interface and provides particulate matter analysis in real time with LabVIEW.

6. REFERENCES

Casella Microdust Pro Real time dust monitor (2008) http://casellausa.com/en/cas/microdust.htm, Accessed: 2009-02-08

Ott, D. N.; Kumar, N. & Peters, T. M. (2007). Passive sampling to capture spatial variability in PM 10-2.5. Athmospheric Environment, Vol. 42, Issue 4, (February 2008), pg. 746-756, 1352-2310

Shorey, R.; Ananda A.; Chan, M.C. & Ooi W. T. (2006). Mobile, Wireless and Sensor Networks: Technology, Applications and Future, John Wiley & Sons, 978-0-47171816-1

*** National Instruments (2008) Using Shared Variables, http://zone.ni.com/devzone/cda/tut/p/id/4679, Accessed: 2009-01-25

*** WiPort Embedded Wireless Device Server (2009) http://www.lantronix.com/device-networking/ embedded-device-servers/wiport.html, Accessed: 2009-03-14