Air purification

Americans spend up to 90% of their time indoors, and in 90% of U.S. offices the number one1)_____ is lack of outdoor air. The EPA estimates that poor indoor air quality results in $60 billion per year in 2)_____expenses. But indoor air quality can be improved by using materials that emit few or no toxins and volatile organic compounds (VOCs), resist 3)_____thereby inhibiting the growth of biological like mold, and adding systems, equipment and products that identify indoor air 4)_____or enhance air quality.

Nanotechnology is contributing to indoor air quality on all of these fronts. Samsung Electronics, for example, has 5)_____ its new Nano e-HEPA (for electric High Efficiency Particulate Arrest) filtration system. The system sifts the air to filter particles, 6)_____ undesirable odors, and kill 7)_____ health threats. It uses a metal 8)_____filter that has been coated with 8-nanometer silver particles. The Kitasato research center of environmental sciences in Japan found the nanofilter killed 99.7% of 9 _____viruses. Up to 98% of odors were eliminated, and another 10)_____eliminated all noxious VOC fumes from paint, varnishes and adhesives.

11 Fill in the gaps in the following passage with a suitable preposition given below: