How do I know a powered respirator is actually working?

This failure mode is specific to powered gear and it is worth understanding.

A sealed mask tells you when it is struggling, because it gets harder to breathe through. A powered hood does not. If the battery dies or the filter blocks, the hood is still on your head and the visor is still down, and it feels much the same. What has changed is that you are no longer getting filtered air pushed past your face.

So the routine is: switch on, feel for airflow, then put it on. Every time.

Two things reduce airflow quietly before they announce themselves. A loading filter makes the blower work harder, and that shows up as shorter battery life first, so if your runtime has dropped over a few months look at the filter rather than the cells. And a blocked mesh pre-filter, which is why blowing it out during cleanup is worth the thirty seconds.

The Breathie Thingy has audible alarms for a clogged filter and a low battery. Trust those over a calendar, and still check for airflow before you put it on.