Portable Detectors

Portable detectors for toxic or flammable gases are essential for use by an emergency response team so that they will know the hazards they are facing when responding to a release. There are many portable analyzers that utilize the fixed-point and sampling system technology described in Sections 6.2.1 and 6.2.2. One other method of portable detection is the use of chemical tubes. 

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Chemical, biological, and radiological detectors—to minimize or prevent harm. Opportunities in the chemical sciences range from the development of rugged, portable detectors for field use to better methods of sample preparation. 

There is no uniform operating procedure for field meters, field portable detectors, and field screening kits because different manufacturers make them in different formats. To use them correctly, we must strictly follow the manufacturer s instructions. When selecting a particular model, we need to evaluate its ruggedness, portability, selectivity, sensitivity, and reliability. To produce usable data, we must have a good understanding of the measurement mechanism, its applicability and limitations, and be concerned with the issues of field instrument calibration and maintenance. In this chapter, we will review some basic general chemistry definitions applicable to field measurements and focus on the common types of field analysis. 

Large area portable detector for the isotopic analysis of weak plutonium and other samples. Measurement of the isotopic composition of weak plutonium samples. 

Figure 10.11 Non-dispersive analyser for measuring CO2 in gaseous media. This assembly is representative of many portable detectors. The selectivity is assured by an adapted optical illter (F2) and by a membrane at the entrance to the cell which only permits gas to pass through to the detector. The assembly contains a second filter (FI) chosen in a non-absorption zone which authorizes to a computation of the transmittance. On the diagram are shown the bandwidths of the two filters and the spectrum as function of transmittance of a gas, here COj. The detectors are thermistors. Left, a chart which presents a choice of wavelengths in the mid-IR and the near IR for several gases (reproduced courtesy of Edinburgh Sensors, GB).

Measurements were made to demonstrate that a portable detector could he used to detect anomalous concentrations of elemental mercury in the air near sites where mercury had been reported in water, sediment, and fish. The Barringer airborne mercury spectrometer was installed in a car, bus, boat, or helicopter. Measurement traverses were made to locate, quantify, and map the anomalous mercury plumes. 

Gas flow proportional counters use a gas ionization detector that produces ionizations as the radiation penetrates the chamber. These are not portable detectors, but they can be used to measure some radiation energies and are able to distinguish between a and p radiation. 

Ground-level surveys can be conducted by vehicle-mounted gamma spectrometers or on foot by handheld or portable detectors. A more detailed map may be obtained by these methods than by aerial mapping, but these are more time consuming and labor intensive. In aerial survey, the distance between the surface and the spectrometer is necessarily larger than ground-level inspection and that is reflected by the sensitivity and resolution. 

The TVA 100B PID Detector is man portable detector utilizes 10.6 eV UV source for photoionization, it co-existed with a companion FID for broader detection capability. The... 

The MiniRae Classic, ppbRae, MiniRAE 2000 detector are handheld portable detector utilizes 10.6ev UV lamp for photo-ionization ionization. 

The MSA Passport II Organic Vapor Monitor is a handheld portable detector utilizes 10.6 eV UV lamp tor photo-ionization ionization. 

Partial body monitoring. Partial body monitoring may be adequate where the radionuchdes of concern tend to be concentrated in a specific organ (e.g. iodine in the thyroid gland) [24]. To measure the activity in a specific organ, a relatively simple measuring set-up (portable detector) may be used. 

Special equipment suitable for hydrocarbon detection must be used when the confined-space atmosphere to be measured has an oxygen content less than 10%. A special portable detector which operates on the thermal-conductivity principle or a laboratory Gas Chromatograph (GC) is preferred for these measurements. 

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