Particle counting is necessary to make cellphones or laptops function properly. These, and many more devices, run on semiconductors which are manufactured by semiconductor companies in clean-rooms with strict standards for air quality.
A clean-room is a work area with an extremely low level of environmental pollutants. The level of contamination in a clean-room must be controlled to conform with a predetermined number of particles per cubic meter, with no particle exceeding a specified size. It is the task of particle counting that ensures compliance with these standards. A clean-room can be as large as an entire factory where the air from the environment is processed to filter out contaminants then recirculated through high efficiency particulate or ultra-low particulate air filters.