National Instruments PXI-1031 User Manual page 32

Chapter 3 Maintenance
Clean the fan filter by washing it in a mild soap solution and then
vacuuming or blowing air through it. Rinse the filter with water and allow
it to dry before reinstalling it on the chassis.
You can replace the fan filter with part number 150139-C from Air
Filtration Products, Inc., Tucson, AZ 85705, if necessary.
© National Instruments Corporation 3-3 NI PXI-1031/PXI-1031DC User Manual