I haven't seen this happen in part because it runs a /long/ time on a battery, but I have seen it when running on a solar panel without enough sunlight. It would fail and reboot every second or so, so the light would blink.
Recently we changed the firmware so that it waits 2-3 seconds to start up. The idea was that it'd try to run for 2-3 seconds, before turning the light on, so that it could "test" whether there's enough power. And if there was, it'd start showing a light. Otherwise, it'd just stay dark (although you may see some of the really tiny lights blinking as it boots up).
That way, if power is too low, it wouldn't annoyingly blink a lot, but rather would reboot over and over but never get to the point where the light goes on. We're still testing how well this works.
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Thanks @Warren (and @Stevie) for this info. Recently I fully charged the battery bar but after plugging in the "traffic light" sensor, the display stayed white even with high generated PM2.5 levels.
Your ability to create a light and small Plantronics sensor-battery combination is nonetheless very interesting: if the sensor could also write data to an SD card (as it does in PurpleAir SD models), I would like to know how much this all weighs and contact my two drone pilot colleagues. If feasible, I think it would be fascinating to measure PM levels at different altitudes and positions relative to a frac sand mine.