I recently spoke with a woman named Becky from 3M who had a lot of questions about the Lighthouse 3016 handheld particle counter. She is looking for a particle counter that can count particles from .3 microns up to 25 microns. I explained that the Lighthouse 3016 could be upgraded to include the 25 micron size for a minimal charge. After answering many of her questions, she asked one I had not heard in a while:

"While looking at the technical specs, I notice that for counting efficiency, it says 50% per JIS… what does that mean?"

I remember asking the same question several years ago, the specification seemed to imply that the unit was only doing half of it’s job. Could this be correct???

The fact is that it is the way particle counters are designed and calibrated. The lowest particle size is always 50% counting efficiency. Lets say we are calibrating the 0.3 micron size - as you run the particles through the sensor, we are looking at the reflected light from each particle. As all 0.3 micron particles are not exactly 0.3 microns (some are 0.2999, and some may 0.3001, etc), you get a bell curve. As you need to have a cut-off point, you select the middle of the "curve" (or the 50% area), and call that 0.3 microns. In reality, the counter is counting all of the 0.3 microns partilces. It’s more of a term than actually describing the efficiency of the counter. This confuses MANY people!!