Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/917400
Healthy Indoors | 27 PM2.5 sensor. Most of these products only integrate sen- sors into a device, they don't manufacture the sensors. Since the sensors in these devices are largely the same, their effectiveness comes down to calibration. Calibration is comparing what a sensor senses against a known quantity. For example, I grew up around very old cars (1910s-1930s) that had very inaccurate speedome- ters. This 1911 Mercedes is one example: To calibrate them, we would take a modern car down the highway next to an old one, match their speeds at an indicat- ed 60 MPH in the modern car, write down what the old car speedometer said, and then go back to the shop and adjust it so 60 was 60. The speedometer was now calibrated. Foobot is the most interesting device for calibration. While it does give readings immediately after being turned on, it says it's calibrating itself for the first 6 days and adjust- ing to its environment. At first, I found it annoying, but after further thought the device gets more respect from me. This leads us to our first comparison between the devices. Fair warning, I'm not a data scientist, so these are definite- ly anecdotal. Further complicating things is the fact that each IAQ monitor has a different combination of sensors. It is diffi- cult to truly compare apples to apples. Here's my attempt: Results — Awareness The Dylos, Foobot, and NetAtMo come out on top. Dylos and NetAtMo do it primarily with novelty. Dylos is the only laser particle sensor and the only one that measures the very small and very dangerous PM0.5. NetAtMo is a weather station with both indoor and outdoor units, and is the only IAQ monitor with this capability. The indoor unit also measures carbon dioxide. In my mind, having on-site readings of outdoor condi- tions (temperature and humidity) helps this device hit above its weight class. Foobot slugs it out by having what I view as the best sensor array and calibration, save the very mediocre CO 2 readings. The CO 2 read- ings don't seem to affect Foobot's "Global Index," or 0-100 score, so it gets a pass on this peccadillo. There are plans to update the faulty algorithm as well. Good readings don't mean a thing if you don't know how to interpret them. This is where software is king. Good software accomplishes a number of things: Consumer IAQ Monitor Sensors and Calibration Comparison Detection Sensitivity & Accuracy Product Cost Temp RH PM0.5 PM2.5 VOC CO 2 CO Overall (Sensors) Air Mentor 6 in 1 $219 A– A– – F A– A – C– Awair $199 A– D – B B A – C** Dylos DC1100 $260 – – A A – – – A–*** Hobo MX1101 $135 A A – – – – – B– Foobot $199 A B+ – B A D* – A NetAtMo $149 A A – – – B – A– Speck $149 A– A– – B+ – – – B– – = Not Available * Foobot derives CO 2 from VOC sensor using an algorithm. It's frustratingly innacurate. ** The humidity monitor being out of calibration drastically threw off Awairs 0-100 score. This degraded the useful ness of the device a great deal, putting my focus on a faulty reading rather than something that was actually wrong. *** The Dylos is the only monitor with a PM0.5 sensor, which senses the very small and very nasty stuff. This fact overrides its lack of other sensors.