Vacuums used in a cleanroom environment require a HEPA (High Efficiency Particulate Air) or ULPA (Ultra Low Particulate Air) filter. The location of the filter inside the vacuum is as critical as the type of filter selected. Stringent contamination standards in the pharmaceutical industries require HEPA/ULPA filters before and after the motor. A filter placed 'downstream' or after the motor eliminates particles created by the motor which would be released back into the cleanroom environment. The filter 'upstream' or before the motor protects the motor from potentially hazardous particles from collecting on the motor. For any cleanroom the HEPA or ULPA filter should be located 'downstream' or after the motor. The motor itself can generate thousands of particles which would be released into the clean environment. A lab envirnoment with less concern for particles may have the HEPA filter located 'upstream' from the motor. Cleanroom World offers a wide variety of vacuum.