Investigation of the Performance of Agricultural Vehicle Cab Filtration Systems

Abstract

The performance of cab filtration systems in agricultural vehicles has been studied: (1) by measurement of the efficiency of the filters, (2) by measurement of air leakage past the filters and (3) by in-cab sampling of dust and micro-organisms, but not pesticides. Filter efficiency has been measured in previous work. In the present work, leakage was measured on-site, using artificially generated aerosols. In-cab sampling was carried out with membrane filter samplers. Cab filters made of cellulose paper or ordinary textile fibres have a low efficiency when new. Electrically charged filters and glass-fibre filters can perform well, although fibre-shedding from glass-fibre filters and limited lifetime of electrically charged filters may cause problems. Leakage of air and fine dust varies between 0·5 % and 30% depending on design. Grain dust concentrations inside cabs during harvesting are usually considerably lower than the limit of 10 mg mr-3 but concentrations of micro-organisms are often much higher than those in other work environments. No evidence was found of significant leakage of dusty air into the cabs through normal air exit routes. Replacement of an old filter by a new one, or of a low efficiency filter by a higher efficiency filter, frequently caused the in-cab dust concentration to increase, indicating clogging or dust dislodgement. A further possibility is that dust may be carried into the cab on the driver's clothing, or that previously introduced dust may be dispersed. The results taken as a whole suggest that the cab/filter system could reasonably achieve a protection factor of 100, where protection factor is defined as the quotient of the concentration of dust immediately outside the cab and the concentration inside.