During use, as dust fills the bag, the bag expands and impinges upon a first of the pressure sensors and then upon {HEAD ~ a second} of {TAIL ~ the pressure sensors}, and so on, thereby indicating a filling of the bag with dust 
of
During use , as dust fills the bag , the bag expands and impinges upon a first of the pressure sensors and then upon { HEAD ~ a second } of { TAIL ~ the pressure sensors } , and so on , thereby indicating a filling of the bag with dust
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH