Pressurized Filter system

PFS what's that?  
Excavating contaminated soils can be hazardous to your health.
The necessity to protect the operator of an excavator against hazardous or toxic substances, during the daily work, is generally accepted. European directives, more cleaning of contaminated soils, terrains around service stations are cleaned, the awareness of these problems is more and more wide spread.

One of the methods to protect the operator of an excavator against polluted ambient air, is to feed filtered, slightly pressurized air into the cabin. The pressure inside the cabin is constantly a little higher then outside, this pressure prevents entrance of contaminated outside air, the filters provide clean breathing air. Pressurized Filter Systems provide filtered air under a slight overpressure. The ultimate pressure depends on the air tightness of the cabin. The pressure difference between the inside and outside of the cabin is just a couple of mbar. (1 mbar=100 Pascal) (The European directive concerning the minimal pressure for a cabin is 100 Pascal for new excavators and 50 Pascal for excavators built before 1/1/1997.) For several reasons the air flow to the cabin must be restricted, this improves the performance and the life span of the filter cartridges (less often necessity to replace the filters!) and the PFS has lesser influence on the cabin temperature. Furthermore it is important that the contact time with the activated carbon is sufficiently high. The air tightness of the cabin is different for each excavator, some excavator cabins can be made air tight with relatively low effort, most cabins require more elaborate modifications to attain the required air tightness.
Click to enlarge.

Click to enlarge.