Are there any plans to add measurements like CO2 to the PA indoor unit?
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I’d love to hear an update on this.
Over the last several years I’ve become more and more engaged in the COVID cautious community, as my wife has a rare blood condition and I also don’t like what I read about long COVID. My air monitoring instincts have served me well in this domain, but one area that is really missing that could be well-suited to PurpleAir devices is an easy way to document the indoor CO2 levels of restaurants and other public spaces. While not a perfect proxy for COVID infectiousness, CO2 levels are a useful indicator when assessing the relative risk of an indoor space. Currently, however, the leading tech for tracking this info across the country seems to be a website where people enter values manually: COVID CO2 tracker. I believe we can do much better with real-time and historical tracking of indoor spaces. Given the real-time live-mapping functionality of PurpleAir, it seems to me that if CO2 sensors were added to the particle and VOC capabilities of the monitors, PurpleAir devices could become quickly the de-facto standard for indoor spaces to broadcast their indoor air quality to the community, particularly the COVID cautious community.
A lot of the COVID cautious community members are using HEPA filters indoors and running around with Aranet4 CO2 monitors (myself included), so there is a lot of overlap with the pollution-related monitoring crowd. I think that many people might be quick to adopt a permanent CO2 monitor that popped up on a map for all to see anytime.
I also remain very interested in cheaper ways to measure ozone, because in addition to HEPA filters, farUVC seems to be promising for dramatically reducing infectious COVID in indoor spaces. Unfortunately, however, the devices also generate ozone. If there was a way to cheaply measure ozone, then the farUVC devices could be coupled with ozone sensors to ensure that the indoor air was actually safe (at least related to ozone levels), instead of guessing based on manufacturer claims.
Thanks for listening…
Always monitoring,
Mark Dixon
I’d love to know if PurpleAir has any information about adding a CO2 monitor to their indoor monitor, or even their Zen.
I think the idea behind adding the Bosch BME68x chips the PA sensors was an effort in this direction. The BME68x, in its default configuration, can sense biological VOCs that can be used as a proxy for CO2. The effectiveness of this measurement needs more development and independent verification, though.
The current state of the art for CO2 sensors requires periodic recalibration by moving the sensor outside or into a controlled area. Not very practical for a consumer device. Some devices approximate this by assuming that if the CO2 level is low in the middle of the day that they must be in an empty building and can recalibrate to an assumed concentration. How accurate this is long term is a question.
More detail on CO2 sensor calibration can be found in this article.
Indoor measurement of ozone would be nice to have, but the technology has a long way to go. Current measurement of ozone for outdoor air quality involves the use of a ozone scrubber, which means the sensor has a chemical that must be replaced periodically. Again, not practical for a consumer device. Hopefully someone will invent a simpler method.
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Is there a way to re-calibrate the device periodically?
Recalibrating the BME68x VOC sensor requires exposing it to the calibration gas mix. Not something you’re doing at home.