PA-I-LED's use of single laser counter

I’m debating whether to buy a PA-I-LED (targeted at indoor use) or one of the outdoor products. The application will always be indoors, but I’m trying to understand the reason most of them have two laser counters, while this one only has one.

After studying the forum, this is what I’ve gathered… The laser counter units can fail in only a few years, at least in outdoor use. It seems the sole reason for having two lasers is to sense that one of them isn’t working properly, through use of redundancy. Maybe the laser can be restored by cleaning, or maybe it needs to be replaced.

Much of the reason for failure appears to be debris or insects. And so it would make sense that the indoor-only product forego a redundant laser unit.

So far, I’d feel comfortable buying it. But there was a third factor for laser failure… “age”:

Other factors can be sensor age or contamination in one channel or the other. The
laser counters have an average lifespan of about two years but can last a lot longer
(or shorter) depending on the conditions under which they operate.
Q: Why is there a gap in the channel readings?

How long can I expect the laser unit to operate reliably even under clean indoor conditions? And how would I know if it wasn’t working anymore?

And how would I know if it wasn’t working anymore?

Are there any sensors on the map around your area?

Note that the PurpleAir Zen can be used indoors…

This one can be used indoors and out with the included desktop or wall (or pole) mount.

Yes. I’m in an urban area, so there are many. And actually, I suppose I could periodically move the PA-I-LED outside and check it against outdoor sensors in the area. Maybe that’s where you were headed.

That would be a hassle though.

Yes, as far as I can tell, any of them can be put indoors, including the Zen. But I liked the cheaper price tag of the PA-I-LED and was trying to understand what I was giving up.

I guess I’m a little surprised this pitfall is left for people to discover accidentally. Maybe this model is intended to compete with cheaper sensors from vendors that don’t have purpleair’s reputation for accuracy, which probably only have a single counter in them. Now that I understand the tradeoff, I’d rather pay more to get two counters.

Well, there is Which Sensor to Choose.

I don’t think you’ll have to put the sensor outside. It obviously depends on the amount of ventilation, and the air quality generally in your city, and of course the temperature outside! Even with all the windows closed, buildings are surprisingly leaky.

I went with the outdoor sensor for my indoor unit as having two particle detectors means you get a continuous checks of the particle detector’s operation as if they begin to differ consistently in reading you know that one or both detectors are no longer giving correct readings. The extra cost of the outdoor unit seemed worth being more sure the reading had a high probability of being correct if both detectors agreed…
Yes the outdoor unit is big and a bit ugly for indoor use but placement in a discreet location solved that issue for me.

Thanks for corroborating that. That’s exactly what I was thinking.

And when they do fail, the FLEX appears to be the only unit allowing you to replace the lasers yourself for $45.

Re: ugliness… I can go for the industrial look. :wink: In any case, it’s worth figuring something out.