Attached are a set of directions for switching the PSL HVAC system between science and commissioning modes. These are also posted at the PSL. In science mode, only the make-up air, the air that pressurizes the PSL to exclude dust, is working, and only at 20% of capacity. In commissioning mode the make-up air is set at 100%, the HEPA fans are turned on to reduce dust, and the air conditioning is turned on to handle the heat load. The 20% make-up air setting does not seem to increase the dust load in the laser room, but the dust load does increase in the anteroom because the HEPA filters are off and there is no overpressure to keep dust from the LVEA out. Figure 1 shows 60 days of dust monitoring in the PSL laser room and the anteroom – most of the plotted time is in full commissioning mode, but the last three days (blue underline) show the dust status in science mode.