tailieunhanh - Air Sampling and Industrial Hygiene Engineering - Chapter 2

Tùy chọn Instrumentation lấy mẫu không khí Chương này chi tiết và thảo luận về các tùy chọn có sẵn để theo dõi chất gây ô nhiễm khác nhau. Nó bao gồm thông tin cho hỗn hợp chất gây ô nhiễm, entanpy nhiệt, nhiễu, và hiệu chuẩn cơ sở. Nó cũng cung cấp các sơ đồ mặt cắt ngang để minh họa các chức năng nội bộ của máy dò khác nhau và các yếu tố cảm biến. 2,1 hợp chất hữu cơ dễ bay hơi mẫu cho các chất hữu cơ dễ bay hơi chủ yếu có nghĩa là lấy. | CHAPTER 2 Air Sampling Instrumentation Options This chapter details and discusses the options available for monitoring various contaminants. It includes information for contaminant mixes thermal enthalpy interferences and basis calibration. It also provides cross-section diagrams to illustrate the internal function of various detector and sensor elements. VOLATILE ORGANIC COMPOUNDS Sampling for volatile organics essentially means sampling for carbon-containing compounds that can get into the air. The term volatile usually means that the chemical gets into the air through a change of phase from liquid to gas. This phase change occurs when temperatures approach equal and exceed the boiling point and continue until equilibrium is established in the environment. For a chemical with a boiling point over 100 F we would not expect to find that chemical volatilizing at room temperatures. A chemical with a boiling point of 75 F on the other hand would be expected to readily volatilize into the environment. Unfortunately like so many rules this one is not always true. Volatilization can imply that the chemical is being transported in the airstream by mechanical means that exposes surface area. An example of this anomaly is mercury which has a boiling point of 674 F. Mercury as a liquid can be dispersed into the airstream as tiny droplets. The phase change occurs around each of these droplets as an equilibrium is established between the mercury liquid and the mercury in the immediate area gas phase. Thus mercury vapor is dispersed into the atmosphere by an equilibrium volatilization phenomenon that is more dependent on mechanical dispersion than on temperature differentials. Photoionization Detector PID Some volatile chemicals can be ionized using light energy. Ionization is based on the creation of electrically charged atoms or molecules and the flow of these positively charged particles toward an electrode. Photoionization Figure is accomplished by applying .