High-Efficiency Particulate Air is a standard of air filter. By this standard an air filter must remove 99.97% of all particles greater than 0.3 micrometre from the air that passes through.
The height represents the vertical dimension of the product. We consider a smaller height better because it assures easy maneuverability.
The width represents the horizontal dimension of the product. We consider a smaller width better because it assures easy maneuverability.
We consider a thinner chassis better because it makes the product more compact and portable. Thinness is a feature highlighted by many manufacturers of mobile devices, but it is essential for a wide range of products.
We consider a lower weight better because lighter devices are more comfortable to carry. A lower weight is also an advantage for home appliances, as it makes transportation easier, and for many other types of products.