氣懸微粒分徑採樣器的研發

Development of Aerosol Size-Selective Devices

國際上，針對目前的採樣器性能標準方面，趨向於採用ACGIH, ISO及CEN協商認可之可呼吸性、胸腔性及可吸入性等三種分徑定義。一般的分徑採樣器雖可以改變採樣流量的方式，達到國際新定義曲線50％截取粒徑之標準，但其採樣效率曲線之斜率仍較為陡峭，因而於小粒徑範圍呈現有高估現象，大粒徑範圍則有低估現象。本研究以不同材質、厚度（5～35 mm）及孔隙度（10～100 pores per inch）的海綿，配合直徑約25 mm的石綿採樣管，作為氣懸微粒採樣時分徑的設備；以DOP和酒石酸鉀鈉作為液態及固態的測試氣懸微粒，且使用經沈降測試腔校準後之氣動直徑偵測儀（APS）量測氣懸微粒。結果發現：單獨改變海綿採樣的表面風速及其厚度、孔隙度、充填密度，或將不同厚度、孔隙度的海綿串聯置放，僅能達到國際新定義曲線50％截取粒徑之要求，而其斜率仍無法與新定義曲線一致。然而利用並聯兩組不同管徑之採樣管，分別置入孔隙度100、lOppi；厚度20、20 mm；直徑25、13 mm之海綿在採樣流量10.1 L/min進行採樣時，可幾近完美地符合可呼吸性微粒部份的新分徑標準。

Rrecent adoption of performance standards for aerosol samplers has been the joint proposal of a compromised definition by the ACGIH, ISO and CEN. By adjusting the sampling flow rate, most of the samplers can only match the 50% cut-size, but not the slope of the sampling efficiency curve of the new international definition. Combinations of foams of different nominal size (10~100 pores per inch), material and thickness (5~35 mm) were used to overcome this bias. The foam disk of 25 mm in diameter was placed in the asbestos sampling cowl. DOP and Potassium Sodium Tartrate (PST) were selected as the liquid and solid test aerosols. An APS was calibrated against a settling chamber and was used to measure the aerosol number concentrations and size distributions upstream and downstream of the foam. The sampling efficiency data showed that the 50% cut-size would be met for the case of foams in series, but the slope is still sharper than the new definition. Nevertheless, the foams in parallel showed great flexibility and many combinations would make the slope flatter, closer to the new international definition. For example, the aerosol penetration through foams in parallel (100 ppi, 20 mm long, diameter of 25 mm + 10 ppi, 20 mm long, diameter of 13 mm) has a nearly perfect match with the respirable fraction of the new international standard, when the total flow rate is set at 10.1 L/min.