Environmental Agricultural Tractor Cab Filter Efficiency and Field Evaluation

摘要

Tractors equipped with environmental enclosures can be used to protect workers from pesticide spray mist and other particulate contaminants. In these cabs, a fan pulls air through filters and then blows this cleaned air into a cab, pressurizing the cab. These enclosures may be used instead of respirators to protect workers from pesticide spray mist. Because such enclosures may be in use for many years, enclosure performance may degrade due to aging and inadequate maintenance. To evaluate the extent to which this occurs, 3-to-4 year old tractor enclosure combinations (cabs retrofitted to tractors after manufacturing) were evaluated at a custom pesticide applicators facility. Optical particle counters were used to measure the aerosol number concentration inside and outside of the cab. The ratio of these concentrations multiplied by 100 is termed percent penetration, the amount of the aerosol which penetrates into the enclosure. For particles in the 0.3 to 0.4 μm range, penetration into the cab was reduced from 11 to 0.4 percent in the following sequential steps. First, manufacturing mistakes were corrected by fixing a bowed flange and inappropriate sealing of the sheet metal used to separate the incoming air from the air which has passed through the filter. This reduced aerosol penetration from 11 to 4.8 percent. When the gasket material on the used filter was replaced with new gasket material, the observed penetration was reduced from 4.8 to 0.65 percent. This suggests that the filter gaskets are deforming and allowing leakage. Also, the filter media were evaluated for aerosol penetration as a function of particle size and the filter media tested per the test criteria stipulated in 42 CFR 84 for negative pressure air purifying particulate respirators. These results indicated that the penetration through the filter media were less than 0.03 percent. Thus, the filter media were not a major source of aerosol leakage into the cab. The results indicate that the manufacturer needs to implement a quality control program to ensure that all cabs meet minimal aerosol penetration criteria into the cabs and that an acceptable maintenance program exists to ensure continued compliance. Furthermore, the degradation of filter gasket material over time needs to be minimized to ensure that the environmental cabs continue to provide acceptable performance.