What information can particle counters provide about particles?

• A. Size
• B. Size and number
• C. Number
• D. Mass

Answer: (B)

Particle counters tell you both how big the particles are and how many there are. They detect particles as they flow past a sensing element (usually by light scattering) and group them into size categories. The output gives the size distribution—how many particles fall into each size range—and the total concentration in the sample. Mass isn’t measured directly; estimating mass would require assuming particle density and shape, so any mass value would be an estimate rather than a direct measurement. This combination of size and count is what lets you understand which particle sizes are present and how abundant they are, important for assessing filtration and overall water quality.