One niche market building service contractors serve is cleanroom areas. These spaces are typically found in manufacturing facilities and the goal is to prevent all but the smallest of particles from entering. Despite the sealed off space, cleanrooms are still susceptible to allergens, dust, skin dander, mold, spores, pollen and bacteria. Cleaning these areas will require the right vacuum.
Cleanrooms range in class from ISO1 to ISO9. A ISO6 class, for example, permits 102 parts at 3 microns; for this (and classes higher than 6) a HEPA vacuum, which collects 99.97 percent of particles at 0.3 microns would suffice.
As the classes get lower, the standard allows 10, 0.1-micron particles, per cubic meter of air. For these levels, contractors would need an ULPA (ultra low penetration air) vacuum, which collects 99.999 percent of particles in the range of 0.1 to 0.2 microns.