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Has anyone tried the Foobot Monitor?

user-2310254 | Posted in General Questions on

Does anyone have experience with this indoor air quality monitor? Are there better alternatives for easily monitoring key indoor pollutants?

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  1. Reid Baldwin | | #1

    I had one for about a month. My purpose was to track particulates and VOCs. Not having any other way to track those things, I am not sure how accurate it is. I was surprised at how low those readings are in my apartment. For temperature and humidity, it tracks the other sources I have well. It calculates CO2 based on other readings. I had read that the CO2 numbers are not trustworthy and I agree. It doesn't track my other CO2 monitor well at all. Since the other CO2 monitor always responds to events in the expected direction, I trust that one rather than the foobot.

  2. charlie_sullivan | | #2

    I've also been considering the "Awair" monitor and the "Air Mentor Pro", both of which include actual CO2 sensors. But I can't decide which to buy.

  3. ERIC WHETZEL | | #4

    I agree with David M., the Energy Smart Ohio article is definitely worth reading.

    In addition, if you're looking to actively counteract indoor pollutants there is research that suggests certain plants can have a significant effect.

    There is a book and a TED talk that you might find interesting:

    How to Grow Fresh Air: 50 Houseplants that Purify Your Home by B.C. Wolverton

    Kamal Meattle: How to Grow Fresh Air (

  4. user-2310254 | | #5

    Thanks, David. The article certainly provides a lot of great information. It looks like I could combine a Foobot, Wemo switch, and a little IFTTT programming and use it to better manage the energy consumption of my Ultra Aire ventilator/dehumidifier. As things are now, the fan portion of the unit is always on. I could probably recoup the $250 of cost over time.

  5. heidner | | #6

    The consumer IAQ monitors - really are not very precise instruments. The drift and repeat-ability even between two of the same models can often vary significantly. They are lower cost for a reason.. There are multiple means of measuring CO2 with sensors. The more accurate method depends on the CO2 spectral absorption (near IR region) Accurate IR CO2 sensors alone can be priced above $100 -- and that's without the electronics to display the value to the consumer, log the results, or power the device. Electrochemical sensors which depend on measuring the resistance of a heated (chemically treated) sensor exposed to gases - are often much lower in price - but they are less specific to a single gas (CO2) and often will sense other gases. The readings may vary with the indoor temp and as the room temp changes.

    CO2 is often used as a proxy for bad indoor air quality - but really in the levels that the sensors work at... (450ppm to 1200ppm) - the CO2 really isn't the bad stuff in the room. It's often the other VOC's that are also climbing up at the same time because the air is stale.

    The better CO2 sensors will automatically adjust themselves back to a baseline condition... typically 450ppm; however for that to be accurate - they really need either fresh air OR to run the new baseline at a point when the CO2 is at the daily min...That can be tough in a house that maintains irregular hours. VOC sensors can AND will eventually become less sensitive... most consumers do not have a means to detect a sensor approaching end-of-life unless they have multiple units in the house and are comparing readings.

    If you've moved the major sources (household chemicals) of the VOC's outside the building envelope - you are still likely to see VOC in a house... perfumes, deodorants, cooking byproducts, byproducts from some paints and inks (marking pens), and finally life itself -- when we pass gas -- we emit VOC's, when we breath, we emit VOC's...

    The big thing is to controlling the chemical storage within the envelope and then after that use the ventilation to replace the by products of human activity. Apply deodorants while in bathroom with fans running... make sure the kitchen stove hood truly vents outside - has a good capture range - and doesn't allow a lot of the cooking fumes to escape into the nearby spaces..

    If you are going to use sensors to control the ventilation (HRV/ERV) in a residence - you need multiple sensors placed near the more common sources of the bad air... and use the readings to adjust and predict the changes in ventilation.

    One more point - generally families spend a large chunk of their time in the bedrooms - sleeping. We (humans still produce VOC while sleeping)... so you will want to monitor the rooms and perhaps increase ventilation in bedrooms as the sensors indicate a need...

  6. user-2310254 | | #7

    Dennis. Great information. So is something like this not worth considering, or is an example of the sort of problems and compromises you detail in your post?

  7. heidner | | #8

    You really have to dig on each item individually to look and see how they are doing the task they specify, and if the device is really capable of doing so accurately over time.

    For the AWAIR, look at the specs

    - Temperature: -40 to +125°C (-40 to +257°F) / +- 0.3°C
    - Humidity: 0 to 95% / +- 3%
    - CO2: 0 to 4000 ppm / +- 75ppm
    - Dust: 0 to 500 μg/m3
    - VOCs

    Look at the humidity range -- 0 to 95%. You can't get below 0, yet the accuracy is 3%. That's probably full scale accuracy -- so it likely means the range is valid from about 3% to about 93%+-2 at the high end. It won't make it to 98-100%, because the sensor would become wet and the raw chip would start reporting really strange results - like negative humidity... or lock up. The Temp sensor is 0.3C, but that is most likely the lowest resolution of the temperature sensor -- probably a RH/T combined sensor. More explanation below...

    They are really listed the raw specs not for their assembled unit but for the sensors - in more or less ideal conditions. The sensor for VOC's really doesn't describe what they detect or the sensitivity. Nor did they specify the sensor design. However if you look at the AWAIR pictures You will see a device that looks a lot like: A Sharp dust sensor -- originally designed for detecting dust in air filters... (not real sensitive) The spec sheet for the Sharp sensor is:

    If you look internally in the Sharp sensor - there is a resistor that heats the air. The purpose is to cause air convection to occur and ensure some air movement through the sensor. That's okay -- BUT -- it also means that the particulate sensor is adding heat into their package at the same time they are trying to measure RH and temp. Most likely they are using a Sensiron SHTxx series, a BOSCH, or Honeywell. All will report incorrect readings if they are in a box that is also adding heat to the enclosure. And then there is the VOC sensor... it looks like it is on its own daughter board with the metal oxide sensor next to the dust sensor (That may be RH/Temp sensor though)... lots of stuff that can interact with each other.

    Nearly all of the consumer devices have the same problems - you can ask if they have NIST traceable certifications available - but that would likely trip the "yup for $500" additional comment - and the specs would then also vary from the generic raw sensor specs.

    The repeatability, accuracy and NIST traceability is why the IAQ instruments from GreyWolf and others cost so much more... they have to be fanatical about the packaging and engineering.

    For DIY... most don't care, but for controlling your indoor ventilation - you want to error on the side of safety... which means that youi'd set any ventilation rates at the current (disputed) ASHRAE recommended values -- and increase the ventilation rates based on sensors that a diminishing air quality in the residence... something that takes a lot of work to do and is generally beyond what most people are interested in.

    About the only think I can suggest on any of the other consumer IAQ units being sold - is look carefully at the specs - and ask them if the unit you buy can include a NIST traceable calibration. If they say NO, that means it really is a consumer "novelty" and it should really have a limited application.

    Sort of tough on the industry ( and I like sensors)... but that's the way it is... They are useful for comparing on how you are doing - if you make changes to lifestyle and move the bad stuff out of the house. But they will not provide accurate enough data to be defensible if you need to argue with companies or contractors about bad products or workmanship (e.g. HVAC bad, bad carpet, etc...)

    BTW, I have bins of gas sensors from multiple vendors... I've built little logging sensors using them for various experiments... they can work well - but the calibration and drift can eat up the savings VS using/renting a commercial unit. If you search internet... there are multiple comparisons of the Sharp sensor with the Dylos ( above consumer grade -- not yet high end lab grade). And there are multiple research papers and studies that compared the drift of various VOC sensors and CO2 sensors....

  8. heidner | | #9

    The CO2 meter is for a NDIR sensor - it uses IR and looks at the absorption at specific light spectra... these tend to be more accurate - but they eat up batteries. Equally important is their reminder:

    "This device will not meet requirements for CO2 monitoring in the NBIC, NFPA, or IFC regulations. The accuracy of the sensor in the TIM10 is not designed for safety situations. Refer to our CO2 Safety Products page for devices that meet your needs. "

    Again if you use a sensor to control ventilation - and it is not certified for the function - you need to assume t will fail -- that means setting ventilation rates at the ASHRAE or appropriate standards - and always adjusting up not down if you think you detect problems..

  9. user-2310254 | | #10

    Dennis. Thank you for providing such a detailed explanation. I now appreciate that monitoring IAC is a much more complicated challenge than I had imagined.

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