ISO 4219-1979 Air quality Determination of gaseous sulphur compounds in ambient air Sampling equipment《空气质量 环境空气中气态硫化物的测定 采样装置》.pdf
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1、International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION*MEYHAPOfiHAR OPAHH3Al connecting tubing; particulate filter and filter holder; absorber; protection filter; sampling pump; gas meter or air-flow regulator. A schematic layout of a typical assembly system is shown in The internal d
2、iameter of the tubing shall be 6 to 8 mm and the figure 1 : internal surface shall be smooth. 5.1 Air intake No particular design of air intake is required for this Inter- national Standard concerning determination of gaseous sulphur compounds only. If the air intake may be exposed to precipitation,
3、 an inverted funnel may be used as protection, as shown in figure 2. If it is intended to carry out other determinations, e.g. concen- tration of black smoke with the same equipment (see clause 21, the air must be drawn in through an air intake of appropriate diameter. 5.2 Connecting tubing 5.2.1 Di
4、mensions Air intake Particulate Absorber Protection filter and filter filter holder Figure 1 - Block diagram of sampling equipment Sampling pump Gas meter or air-flow regulator - Protecting funnel Figure 2 - Air intake with protecting funnel IS0 4219-1979 (E) 5.2.2 Material In addition to the genera
5、l requirements for materials, plastics materials used shall be protected from actinic activity and preferably should be covered with a material having a low ther- mal conductivity. All tubing shall be airtight. Regular cleaning of the tubing is recommended. The following materials, in order of prefe
6、rence according to descending effectiveness, may be used : a) Polytetrafluorethylene (PTFE). Although chemically inert, PTFE is not flexible and difficulty may be experienced in making connections. Connections with PTFE can be made successfully using connectors which are available in PTFE. In additi
7、on, in view of the inflexibility of PTFE, there is no need to use PTFE downstream of the sample absorber. Rubber vacuum hose should be the preferred material since it is flexible, makes good seals and will not affect the sample because the components of interest have already been removed. b) Glass.
8、Glass is fragile. It is suggested that connections to components be made using butt joints with flexible PVC tubing. c) Polypropylene (polyethylene). Agents used for cleaning tubing shall 5.3 Particulate filter be sulphur free. The assembly shall be airtight in use; hence, an appropriate clamping de
9、vice shall be used together with an annular seal. Air shall be drawn upwards through the filter. 5.3.1 Filter material The material of the filter shall be chemically inert with respect to sulphur compounds, and shall not be hygroscopic. The filter shall possess high efficiency (99 %I for particles a
10、bove 0,3 pm. If the filter is being used simply to remove particulate matter (which interferes with some methods of analysis), a suitable filter is a pad of polystyrene fibrest). This filter has excellent efficiency and low pressure drop, and the material is inert. Other kinds of inert filter can al
11、so be used. The use of glass fibre filter material is not recommended as it is too reactive (see first paragraph). NOTE - Under conditions of high humidity, the particulate filter may become damp and thus absorb some sulphur compounds from the air passing through it. These conditions should be noted
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