P. Görner

Field Comparison of 37-mm Closed-Face Cassettes and IOM Samplers

On examining the published results of comparisons of sampling with Institute of Occupational Medicine (IOM) (Edinburgh, U.K.) samplers and 37-mm closed-face cassettes it was observed that they usually do not take into account the dust deposited on the walls of the cassettes. As the method used by the Institut National de Recherche et de Sécurité, France (INRS), to analyze metals includes the analysis of these deposits, it was decided to evaluate the differences obtained between these samplers when using this method. The essays were conducted in three different plants, and repetitive static samplings were carried out to compare 2 L/min, IOM cassettes and 1 or 2 L/min 37-mm closed-face cassettes. The airborne particles were also sampled simultaneously for granulometric analysis. Gravimetric determinations of sampled aerosol were obtained by weighing 37-mm filters and IOM cassettes, and the aerosol collected on the filters and the particles deposited on the walls were analyzed separately for both types of samplers by atomic spectrometry for metals content. The intra-sampler variability and inter-sampler ratios were then determined. Although results obtained for gravimetric analysis are comparable to those published elsewhere (ratio IOM/37-mm much higher than 1), the metal analysis revealed a close agreement between the results obtained with the three sampling methods tested when the wall deposits were taken into account. As published previously, the ratio of wall deposits to filter collected aerosol for 37-mm cassettes is variable, and it would appear to be very difficult to find an appropriate correction factor applicable when only the filter is analyzed. Were these results to be confirmed by further experiments, sampling with 37-mm closed-faced at 1 or 2 L/min or with an IOM sampler would be equivalent for all pollutants for which the analytical method allows the recovery of walls deposit.

Bioaerosol sampling by a personal rotating cup sampler CIP 10-M

High concentrations of bioaerosols containing bacterial, fungal and biotoxinic matter are encountered in many workplaces, e.g. solid waste treatment plants, waste water treatment plants and sewage networks. A personal bioaerosol sampler, the CIP 10-M (M-microbiologic), has been developed to measure worker exposure to airborne biological agents. This sampler is battery operated; it is light and easy to wear and offers full work shift autonomy. It can sample much higher concentrations than biological impactors and limits the mechanical stress on the microorganisms. Biological particles are collected in 2 ml of liquid medium inside a rotating cup fitted with radial vanes to maintain an air flow rate of 10 l min(-1) at a rotational speed of approximately 7,000 rpm. The rotating cup is made of sterilisable material. The sampled particles follow a helicoidal trajectory as they are pushed to the surface of the liquid by centrifugal force, which creates a thin vertical liquid layer. Sterile water or another collecting liquid can be used. Three particle size selectors allow health-related aerosol fractions to be sampled according to international conventions. The sampled microbiological particles can be easily recovered for counting, incubation or further biochemical analysis, e.g., for airborne endotoxins. Its physical sampling efficiency was laboratory tested and field trials were carried out in industrial waste management conditions. The results indicate satisfactory collection efficiency, whilst experimental application has demonstrated the usefulness of the CIP 10-M personal sampler for individual bioaerosol exposure monitoring.

Investigation and application of a model for porous foam aerosol penetration

Measurements of aerosol penetration through porous polyurethane foam plugs were carried out in order to develop a model describing the aerosol penetration behaviour. The data were found agree well with an existing semi-empirical model for porous foam aerosol penetration. This model was improved by reformulating it to use consistent units, and accurately measurable input parameters. The model was implemented as part of a design spreadsheet, to design foam modules suitable for a range of specific aerosol monitoring applications. The design spreadsheet was validated by comparing its outputs with the known characteristics of a number of pre-existing foam modules. It predicted the characteristics of these modules accurately, within the limitations due to a lack of knowledge of the precise cell diameters of the foams used to make them. The use of the design spreadsheet to explore different options for size-selective foam modules is illustrated. The results obtained highlight the importance of a reliable supply of foam, having closely specified cell diameters, in order to manufacture size-selective samplers meeting acceptable quality standards.

Personal thoracic CIP10-T sampler and its static version Cathia-T

A specific version of the personal aerosol sampler CIP 10 was designed, named CIP10-T, for sampling the conventional CEN thoracic fraction. A static sampler, named CATHIA, was also designed. It uses the same sampling head, but the size selected particles are collected onto a filter. The combined particle efficiency of the aspiration slot and the selector was measured in a horizontal wind tunnel at low air velocity, close to 16 cm s-1. The flow rate of both samplers was fixed at its nominal value, i.e., 71 min-1. Two different methods were used: the former was based on the Aerodynamic Particle Sizer (TSI); the latter used the measurement of particle size distribution of the collected samples by the Coulter technique. For the CIP10-T sampler, the particle collection efficiency onto the rotating cup was also measured. For both samplers bias and accuracy maps have been calculated, following the recommendations of a new CEN standard about sampler performance. The bias does not exceed 10% in absolute value for both samplers, within a large range of particle size distribution of the total aerosol. For the CIP10-T sampler, the accuracy map exhibits a large area where the accuracy is better than 10%, corresponding for example to 4 microns < or = MMAD < or = 14 microns for GSD = 2. For the same geometric standard deviation, the accuracy is still better than 20% for 15 microns < or = MMAD < or = 21 microns. For the CATHIA-T sampler, the accuracy map can be roughly divided into two parts. The accuracy remains better than 10% for MMAD < or = 12 microns, and it remains between 10 and 20% for coarser aerosols, with 13 microns < or = MMAD < or = 20 microns, provided GSD > or = 2.

A new experimental wind tunnel facility for aerosol sampling investigations

Abstract A new experimental wind tunnel facility for aerosol sampling investigations has been built and its performance evaluated. Subsequently, an experimental methodology using a polydisperse test aerosol of glass beads to measure entry, transmission and overall sampling efficiencies has been developed and tested. The new facility is composed of a horizontal cylindrical pipe of 5 m long and 30 cm in diameter. The measurement zone is located just at the exit, allowing to take benefit of the whole cross-sectional area inside a stabilised aerosol flow. The working air velocity range is 0.5–4.5 m s−1 Air velocity and turbulence profiles are uniform within 10%. Turbulence in the working section is controlled with a square mesh grid. The test aerosol is generated by a fluidized-bed generator and dispersed into the clean air flow upstream of the horizontal part. Generated particles are within a size interval extending from a few μm to about 80 μm in aerodynamic diameter. Tests of time and space stability of the test aerosol in the working section were carried out. They have shown a reasonably uniform spatial distribution and time stability considering the size range of generated particles. The experimental method allows to obtain, simultaneously with the same technique entry, transmission, and overall sampling efficiencies of samplers from several μm up to 70 μm in particle aerodynamic diameter with a good accuracy. It is based on the measurement of the distribution of particle number concentration vs particle aerodynamic diameter of deposited and sampled aerosols in a reference probe and in the test sampler. To evaluate both the new wind tunnel facility and the methodology, measurements of the different efficiencies were achieved using a cylindrical sharp-edged thin-walled probe as a test sampler. This evaluation was performed in three steps. At first, the reproducibility of transmission efficiency measurements of the probe working in isokinetic conditions was determined. It appears fairly good between 10 and 70 μm in particle aerodynamic diameter. Then, the methodology was applied to the assessment of the aspiration efficiency of a probe working in subisokinetic conditions. Finally, a consistency test of the data was proposed and applied to our data; it consists in comparing the mass fractions of collected samples (deposited on the internal sampler walls, collected onto filters) calculated from the efficiency data and the distributions of particle concentrations, with those which are directly recovered after each experiment and weighed. This test yields an indicator of the quality of the whole efficiency data set.

Site Comparison of Selected Aerosol Samplers in the Wood Industry

Several samplers (IOM, CIP 10-I v1, ACCU-CAP, and Button) were evaluated at various wood industry companies using the CALTOOL system. The results obtained show that compared to the CALTOOL mouth, which can be considered to be representative of the exposure of a person placed at the same location under the same experimental conditions, the concentrations measured by the IOM, CIP 10-I v1, and ACCU-CAP samplers are not significantly different (respectively, 1.12, 0.94, and 0.80 compared to 1.00), the Button sampler (0.86) being close to the ACCU-CAP sampler. Comparisons of dust concentrations measured using both a closed-face cassette (CFC) and one of the above samplers were also made. In all, 235 sampling pairs (sampler + CFC) taken at six companies provided us with a comparison of concentrations measured using IOM, CIP 10-I v1, ACCU-CAP, and Button samplers with concentrations measured using a CFC. All the studied samplers collected systematically more dust than the CFC (2.0 times more for the IOM sampler, 1.84 times more for the CIP 10-I v1 sampler, 1.68 times more for the ACCU-CAP sampler, and 1.46 times more for the Button sampler). The literature most frequently compares the IOM sampler with the CFC: published results generally show larger differences compared with the CFC than those found during our research. There are several explanations for this difference, one of which involves CFC orientation during sampling. It has been shown that concentrations measured using a CFC are dependent on its orientation. Different CFC positions from one sampling session to another are therefore likely to cause differences during CFC-IOM sampler comparisons.

Generalized theory of dispersion forces

Abstract The analytical integration of the Overbeek potential for two interacting bodies is carried out. By applying dimensional analysis and finding the suitable dimensionless parameters, generalized and simplified expressions for attraction energy are derived. The regions of integration are transformed in order to determine directly the distance between interacting particles. The physical interpretation of the generalized theory and its simultaneous validity for the sphere-sphere and sphere-plate geometrical models at arbitrary distances is shown. By limiting approximation of certain dimensionless parameters the theory can be reduced to the special theories of Hamaker or Van Shilfhout for short or long distance interactions, respectively. Finally, the relationship between the Hamaker constant and the retarded Hamaker constant was found.

Annular aspiration slot entry efficiency of the CIP-10 aerosol sampler

The CIP-10 personal or static aerosol sampler is designed to sample the respirable, thoracic or inhalable aerosol fraction by using the appropriate selector. All these versions have the same downward-oriented annular aspiration slot. The annular slot entry efficiency at a flow rate of 10 l min–1 was studied as a static sampler in an experimental wind tunnel, at first for a 1 m s–1 wind velocity. Glass beads were generated as a test aerosol by a fluidized bed aerosol generator. A sharp-edged thin-walled isokinetic probe was used for reference sampling. The particle size-dependent efficiency was deduced from the particle size distributions of both reference and annular slot samples. Particle size distributions were measured as functions of the volume equivalent diameter Dv by the Coulter Multisizer technique. The aerodynamic particle diameter Dae was deduced from Dv by using particle density and Reynolds number. The entry efficiency of the CIP-10 annular aspiration slot at 1 m s–1 is between 0.9 and 0.4 for the whole range of particle aerodynamic diameters within the range 10–60 µm. By minimizing the inner particle deposit under the protecting cup of the selector, the instrument can meet the CEN sampling criteria for sampling of inhalable aerosol as shown on the bias and accuracy maps.

Sampling Efficiency and Performance of Selected Thoracic Aerosol Samplers

Measurement of worker exposure to a thoracic health-related aerosol fraction is necessary in a number of occupational situations. This is the case of workplaces with atmospheres polluted by fibrous particles, such as cotton dust or asbestos, and by particles inducing irritation or bronchoconstriction such as acid mists or flour dust. Three personal and two static thoracic aerosol samplers were tested under laboratory conditions. Sampling efficiency with respect to particle aerodynamic diameter was measured in a horizontal low wind tunnel and in a vertical calm air chamber. Sampling performance was evaluated against conventional thoracic penetration. Three of the tested samplers performed well, when sampling the thoracic aerosol at nominal flow rate and two others performed well at optimized flow rate. The limit of flow rate optimization was found when using cyclone samplers.

Physical performances and kinetics of evaporation of the CIP 10-M personal sampler's rotating cup containing aqueous or viscous collection fluid

ABSTRACT The CIP 10-M personal sampler measures worker exposure to airborne particles by collecting particles in a rotating metal cup containing a few milliliters of a collection fluid. This device is mainly used to sample microorganisms or microbial components to measure bioaerosol concentrations in various occupational environments. Aqueous liquids are generally used, but their rapid evaporation limits the duration of sampling; alternative collection fluids could alleviate this problem. Indeed, the particle-collection efficiency of the rotating cup has not been extensively studied, and the only data available relate to a discontinued model. This study aimed to measure the collection efficiency of the current rotating cup model containing an aqueous (water) or viscous (ViaTrap mineral oil) collection fluid. The kinetics of evaporation confirmed that ViaTrap does not evaporate, making 8-h sampling campaigns in constant volumes feasible. Particles with a wide range of aerodynamic diameters (between around 0.1 and 10 µm) were produced using various test rigs and mono- or polydisperse test aerosols. Both new and older cup models performed similarly, with a collection efficiency of >80% for larger particles (aerodynamic diameters >2.8 µm), progressively decreasing to around 50% for aerodynamic diameters of 2.1 µm; with aerodynamic diameters of <1 µm, the collection efficiency was generally <10%. In physical terms, collection efficiency was unaffected by the type (aqueous or viscous) or volume (between 0 and 3 mL) of collection fluid used. Bias maps indicated that the inhalable fraction may be underestimated in occupational settings, particularly with aerosols mainly composed of particles with aerodynamic diameters of less than around 3 µm. Copyright