Determination of permeability of ultra-fine cupric oxide aerosol through military filters and protective filters

Introduction The paper evaluates the filtration and sorption efficiency of selected types of military combined filters and protective filters using the methodology and instrumentation introduced in the accredited laboratories... [ view full abstract ]

Introduction

The paper evaluates the filtration and sorption efficiency of selected types of military combined filters and protective filters using the methodology and instrumentation introduced in the accredited laboratories of the Institute of Analytical Chemistry of the Czech Academy of Sciences.

Methods

The testing was carried out with the use of ultra-fine aerosol containing cupric oxide nanoparticles ranging in size from 7.6 nm to 299.6 nm. Nanoparticles were generated in situ in a hot flow tubular reactor using the evaporation-oxidation-condensation technique. The resulting metal vapours were oxidised to cupric oxide after dilution with air. During the measurement, the aerosol flow rate was set to 96 l/min. The measurements of nanoparticles were carried out using a scanning mobility particle sizer before and after the passage through the filter and a specially developed sampling device at one level of concentration (total particle number concentration before entering the filters was approximately 750000 particles/cm³). Samples were obtained four times in five minute intervals (in 10,15,20 and 25 minutes).

Results

The basic parameters of permeability of ultra-fine aerosol passing through the tested material were evaluated, in particular particle size, mass and volume distribution, efficiency of nanoparticle capture by filter, nanoparticle penetration through filter and overall filtration efficiency.

Discussion

The obtained measurement results have shown that the filtration efficiency over the entire measured range of nanoparticles was sufficient; however, it was different for particular particle sizes. The reason is probably the combination of surface and depth particle trapping mechanisms. The results of the total particle number concentration of the aerosol after the passage through the tested filters ranged from 0 to 6.59 particles/cm³ (i.e. from 0 to 0.000871% of the original concentration). The results of the paper will be used for evaluating the quality of military protection filters used in the Armed Forces of the Czech Republic in military training and in the course of work of military formations at the specialized workplaces. The structure of filters used in the Fire Rescue Service is very similar to that of the military filters. The results, therefore, will also be used in the field of safety.