TJ and I cleaned the BSC2 aluminum floor, the bottom of the chamber below that, feedthrough nozzles, support tubes and their nozzles (see figure for photo of cleaning and some of the stuff we found). The particulate level while walking around gently did not change significantly from before to after the cleaning (see table below). This and the other cleaning experiments reported in the table suggest that, at the current state of cleanliness, the dominant source of suspended particulate is the people and the things we bring in rather than dust that we stir up by moving around.
The dust counts generally returned to low levels a minute or two after the activities in the table.
Just as patting clothes produces more dust, we found that rapid movements produce more dust in the chamber than slow movements. The linked video shows the movement speed and the wiping speed that produced the lower levels in the table below: slow chamber speed.
Recommendations:
1. The chambers are currently clean enough that general cleaning is probably counterproductive.
2. Move slowly when possible. This can reduce the particulate suspended from your bunny suit by an order of magnitude.
|
Activity |
Particulate per cubic foot* |
|
|
0.3 um |
0.5 um |
|
|
Standing still in chamber |
0 |
0 |
|
Walking around gently in BSC2 before cleaning |
150 |
80 |
|
Walking around gently in BSC2 an hour after cleaning aluminum floor, bottom of chamber, and all nozzles |
170 |
85 |
|
Wiping aluminum BSC chamber floor |
200 |
50 |
|
Wiping feedthroughs and their nozzles |
200 |
70 |
|
Cleaning support tubes and their nozzles |
100 |
60 |
|
Slow wiping of BSC floor under aluminum floor towards center (lowest part) |
200 |
50 |
|
Fast wiping of BSC floor under aluminum floor towards center (lowest part) |
800 |
500 |
|
Deploying vacuum hose and accessories |
1000 |
800 |
|
Vacuuming up material wiped to center of BSC floor |
200 |
50 |
|
Vacuuming bellows with tube accesory that fits between them |
600 |
150 |
|
Vacuuming walls in spool piece |
200 |
50 |
|
Vacuuming aluminum floor in chamber while hose assembly is dragging |
600 |
200 |
|
Waving hand up and down while standing still outside the chamber |
150 |
50 |
|
Waving hand up and down while standing still inside the chamber, monitor at same relative position |
200 |
70 |
* Particle counts are aproximate averages, mostly of 1 minute samples. Repeats suggested that differences in the table of a factor of two or greater are significant. Quiet controls were taken in between reported measurements to ensure that measured levels were not significantly affected by previous activities. Monitor: Met One GT-521S laser particle counter
TJ and Robert
