Hide Dust hides smaller blobs (disconnected parts) of a surface. One use is to simplify the display of noisy volume data. See also: Volume Filter, Measure and Color Blobs
There are several ways to start Hide Dust, a tool in the Volume Data category (including from the Volume Viewer Tools menu).
The surface of interest should be displayed and then chosen from the Surface menu. Blobs can be measured in various ways; the cutoff value and slider refer to the method specified in the options.
Nothing will happen until Hide is clicked. Clicking Hide limits the display of the chosen surface using the current settings and initiates automatic updates of that surface as the cutoff or measurement method is changed. The cutoff can be changed by typing a new value or dragging the slider. Changes affect only the currently chosen surface. Choosing another surface from the menu suspends updating of the previously chosen surface, but its cutoff and measurement method will be retained until it is unhidden. It is necessary to click Hide again to initiate automatic updating of the newly chosen surface (unless previously initiated). Clicking Unhide stops hiding blobs of the currently chosen surface and halts its automatic updates.
Clicking Options reveals the measurement setting
(clicking the close button 
on the right
hides it again):