Counter condensation nucleus

The activity concentration of radon and of the free and aerosol attached radon daughters i/ere measured simultaneously. During these measurements the aerosol particle concentration i/as registered by means of a condensation nuclei counter (General Electric). 

The rooms without aerosol sources and low ventilation rate (v<0.3 hf1 ) had low aerosol concentrations (2 103 - 104 cm-3) due to the small influence of the higher aerosol concentrations outdoors (aerosols by traffic and combustions) (Table la). In this case the aerosol in the room air was aged by coagulation and plateout and had less condensation nuclei of smaller sizes (d<100 nm). Rooms with a moderate ventilation show higher particle concentrations ((1-5) 10 cm 3) (Table Ila). With aerosol sources in a room (Table III) the aerosol concentrations can increase to 5 105 particles/cm3. The relative error of the measured particle concentration is in the order of 15% primary determined by the uncertainties of the absolute calibrations of the condensation nuclei counter. 

Ararwal, J.K. and G.J. Sem, Continuous Flow, Single-Particle-Counting Condensation Nuclei Counter, J. Aerosol Sci. 11 343-358 (1980). 

However, these results are probably the result of the method of detecting particles and thereby provide an operational definition of "particle". All of these studies use a condensation nuclei counter to determine the presence of "particles". These devices have been found to have sharply decreasing efficiency for detecting particles less than 0.01 ym (Leong, et al., 1983, for example). 

A TSI Condensation Nuclei Counter model 3020 is used to continuously monitor the aerosol concentration in the chamber atmosphere. The chamber air is drawn through a port in the chamber wall into the counter and returned to the chamber through another port. The chamber interior temperature and humidity are monitored with a commercial hygrometer system. 

Errors may be due to the instrumentation itself. Improper calibration of condensation nuclei counters may lead to poor nuclei concen-... 

Condensation nuclei counter growth in alcohol-saturated chamber optical particle counting 37... 

Particle Number Concentration and Size Distribution. The development of aerosol science to its present state has been directly tied to the available instrumentation. The introduction of the Aitken condensation nuclei counter in the late 1800s marks the beginning of aerosol science by the ability to measure number concentrations (4). Theoretical descriptions of the change in the number concentration by coagulation quickly followed. Particle size distribution measurements became possible when the cascade impactor was developed, and its development allowed the validation of predictions that could not previously be tested. The cascade impactor was originally introduced by May (5, 6), and a wide variety of impactors have since been used. Operated at atmospheric pressure and with jets fabricated by conventional machining, most impactors can only classify particles larger... 

Next, the sampling flow was guided to different measurement instruments. The concentration number and the size distribution of submicron particles (0.01-0.5 pm) was obtained with a TSI Scanning Mobility Particle Sizer (SMPS) consisting of a differential electrical mobility analyzer coupled with a condensation nuclei counter. Previously a preconditioning gas system was used. This basically consists of a cyclon,... 

For a poiydisperse aerosol, the number of particles deposited up to any point in the system can be calculated from the theory for monodisperse aerosols and then integrating over the initial. size distribution, which is the quantity sought- The experimental measure ments made with the condensation nuclei counter gives the number concentration of the poiydisperse aerosol as a function of the distance from the inlet to the diffusion battery. The recovery of the size distribution function from the measured decay In particle concentration can be accomplished in an approximate way. Various numerical schemes based on plausible approximations have been developed to accomplish the inversion (Cheng, 1993). The lower detection limit for the diffusion battery is 2 to 5 nm. Systems are not difficult to build for specific applications or can be purchased commercially. 

A schematic diagram of the apparatus for TPA measurements is shown in Figure 8.40. The polymer samples, 1 x 0.125 0.014 in., were heated in a copper tube furnace thai was programmed for a temperature rise of 50cC/h. Hydrogen was passed over the sample at a 3 mL sec flow rate, but because the condensation nuclei counter required a gas flow of lOOmL/s, additional amounts of nitrogen were added beyond the furnace and heat exchangers. Some materials studied by this technique are shown in Table 8.7. 

The M41 Protection Assessment Test System (PATS) was fielded to validate the protection afforded by the M40, M42, and M17 series masks (Figure 16-4). The PATS is a miniature, continuous flow, condensation nuclei counter. It samples particles from ambient air and compares them with particles in the air contained inside the wearer s mask. The resulting numerical values are then used to determine the protection factor (PF) of the mask. The result of the pass/fail test is determined by the mask s ability to provide a PF of 1,667 or greater, which is the minimum army requirement. The PATS ensures that the mask is the proper size for the individual wearer, and that there are no critical leaks in the mask system due to missing or defective parts or improper maintenance. 

Cle, S. L. Interactive comment on Calibration and measurement uncertainties of a continuous-flow cloud condensation nuclei counter (DMT-CCNC) CCN activation of ammonium sulfate and sodium chloride aerosol particles in theory and experiments by D. Rose et al., Atmos. Chem. Phys. Discuss., 7, S4180-S4183, 2007. 

Ambient aerosol condensation nuclei counter (CNC) quantitative fit testing protocol. 

The ambient aerosol condensation nuclei counter (CNC) quantitative fit testing (Portacount ) protocol quantitatively fit tests respirators with the use of a probe. 

Figure 5.6 shows the unattached fraction of radon (/ ,Rn) and thoron (/p,Tn) decay products as a function of the particle concentration of atmospheric aerosols. The fp values as a function of the particle concentration, Z, are measured by means of a condensation nuclei counter (CNC). Many working places have aerosol sources due to human activities and combustion and technical processes with a high particle concentration, Z > 4 X 10 particles cm , and therefore fp values below 0.01. The fp values are higher than 0.1 for places with particle concentrations <4 x 10 particles cm . This is the case in poorly ventilated rooms (ventilation rate <0.5 h ) without additional aerosol sources, rooms with an operating air cleaner and poorly ventilated underground caves. For the unattached thoron decay products in indoor air, the unattached fraction is estimated by the equation... 

Cloud condensation nuclei counter (CNC)—lower size limit depends on supersaturation and design measures part of nuclei mode and most of accumulation mode 0.01 1 100 cm Condensation—low siq)ersati]ration 1 f... 

Fig. 6.21. Continuous flow condensation nuclei counter, side view. N = nuclei inlet A = alcohol tube AP = alcohol pool O = orifices C = cold tube LB = light bulb L = lens PC = photocell E = exhaust F = flow meter P = pump I = thermal insulation D = drain.

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