Creating a new air quality monitor. Do you have advice?

[yan azdoud]

Hi All,
I am new on the forum.

I am building a smart air quality monitor that can pair with wifi and smart home appliance and give advice for better ventilation/ source mitigation. The device monitors T/Rh, particulate matter (1, 2.5 and 10 um), CO and TVOC. The PM and CO sensor are reliable and EPA tested, the TVOC is general and useful for tracking spills/leaks of volatile chemicals and use of solvent containing cleaners/paints.

I believe that this device can be useful if installed by HVAC professional to improve airflow, trigger filter change and improve overall confort. Do you think that this would be useful for you guys? I am looking for partners for upsales directly at install job. The advantage of the device is that it can tell you when the filters need changing (by monitoring the efficiency of air pollutant removal), which can create a recurring income for the installer/ maintenance crew.

If you have more idea on how to use this device, let me know. I am currently running a pre-sale on my website (meetclair) for a Beta test to improve the end-user experience.

All advice welcome!


Yan

[randyf]

Hi All,
I am new on the forum.

I am building a smart air quality monitor that can pair with wifi and smart home appliance and give advice for better ventilation/ source mitigation. The device monitors T/Rh, particulate matter (1, 2.5 and 10 um), CO and TVOC. The PM and CO sensor are reliable and EPA tested, the TVOC is general and useful for tracking spills/leaks of volatile chemicals and use of solvent containing cleaners/paints.

I believe that this device can be useful if installed by HVAC professional to improve airflow, trigger filter change and improve overall confort. Do you think that this would be useful for you guys? I am looking for partners for upsales directly at install job. The advantage of the device is that it can tell you when the filters need changing (by monitoring the efficiency of air pollutant removal), which can create a recurring income for the installer/ maintenance crew.

If you have more idea on how to use this device, let me know. I am currently running a pre-sale on my website (meetclair) for a Beta test to improve the end-user experience.

All advice welcome!


Yan

I'm interested in TVOC measurements and have some experience using PID meters and gas chromatography. I have not be impressed by MOS technology used in a number of consumer products and offered in very inexpensive modules. If you have any info to on the reliability of this devices (MOS technology) I'd be very interested. All the implementation I've seen are not useful.

When I need to read TVOC levels I use a ppbRAE or if more detail is needed I use and independent lab for gas chromatography/mass spec.

[HVAC_Marc]

I believe that this device can be useful if installed by HVAC professional to improve airflow, trigger filter change and improve overall confort.

It's not going to do tiddly to improve airflow. It wont affect filter changes. Comfort is debatable.

[randyf]

It's not going to do tiddly to improve airflow. It wont affect filter changes. Comfort is debatable.

He wasn't talking about a device to improve air flow or air quality, he was talking about a device to measure air quality that would indicate when air flow and filter changes would be needed.
I'm only interested in TVOC measurements and from what I've seen the recent batch of inexpensive devices that use MOS semiconductor for TVOC readings are not useful. I was hoping otherwise cause PID meters and lab testing in expensive and can be time consuming. Particulates and RH can be measured accurately (Dylos Meter is very accurate and not that expensive) and relatively inexpensively.

[yan azdoud]

Hey Marc,

It's not going to do tiddly to improve airflow.

The device itself only measure and eventually control if a smart thermostat is installed. By "improve airflow" I meant run or advice to run the system on fan when necessary. By necessary I mean when a high concentration of PM is detected. VOCs and CO need to be vented outside so other mitigation methods will be proposed, and an alert given, especially for CO.

It wont affect filter changes.

Actually I think it may, but that remain to be tested on various systems. My rationale is that overall effectiveness of the HVAC system at venting a unit varies with filter clogging. The venting efficiency in turn impacts the effectiveness at removing particulate from a room. By comparing the evacuation rate of particulate based on past performance for a given concentration can help for predicting filter change rate, which may be earlier or later than what the filter manufacturer recommends. This may not matter for large system where the building manager will just pay for the filter to be changed on a fixed schedule, but it may help for family units. Let me know if there are practical flaws in this argument.

Comfort is debatable.

Indeed. It will depend on the unit and the user. For instance, if you have allergies to dustmites/mold/pollen/smoke, advice and automation of venting can improve the quality of life and comfort of the user. I personally have allergies and asthma and I have observed clear correlation between smoke concentration from cooking and allergic reaction 6 hours later. If you have an air purifier/ humidifier or dehumidifier, the device can also control smart plugs and turn these device on or off based on its internal logic, concentration of pollutant and temperature and humidity.

[yan azdoud]

I'm only interested in TVOC measurements and from what I've seen the recent batch of inexpensive devices that use MOS semiconductor for TVOC readings are not useful.

I agree, I had trouble finding a relevant TVOC sensor. I settled on the latest by Sensorion (SGP30) as it shows relatively good stability in time and is way more reliable than the bosh sensor or the CCS118. That being said, still a MOS sensor. The sensor also calibrate its internal zero at startup, which means that you have to start it in "clean air" (less than 100ppb) and keep it powered. The actual accuracy I noticed is about +-100ppb, which is not useful if you want to measure species like formaldehyde. It is however interesting in high VOC environments (like when solvent are used, like when cleaning, painting, caulking etc) which is how I plan to use this. It also does eCO2, but that is a joke (really a measure of H2, not relevant in places where sources of CO2 other than humans exist).
As for PM, I use a sensor in the same precision range as the Dylos. the overall cost of my device is less though.

What kind of VOC are you interested in? I have a fair amount of expertise in low cost sensors and calibration.

[randyf]

I agree, I had trouble finding a relevant TVOC sensor. I settled on the latest by Sensorion (SGP30) as it shows relatively good stability in time and is way more reliable than the bosh sensor or the CCS118. That being said, still a MOS sensor. The sensor also calibrate its internal zero at startup, which means that you have to start it in "clean air" (less than 100ppb) and keep it powered. The actual accuracy I noticed is about +-100ppb, which is not useful if you want to measure species like formaldehyde. It is however interesting in high VOC environments (like when solvent are used, like when cleaning, painting, caulking etc) which is how I plan to use this. It also does eCO2, but that is a joke (really a measure of H2, not relevant in places where sources of CO2 other than humans exist).
As for PM, I use a sensor in the same precision range as the Dylos. the overall cost of my device is less though.

What kind of VOC are you interested in? I have a fair amount of expertise in low cost sensors and calibration.

Hi Yan,
Glad you have chimed in. I've been looking for someone that has some technical experience with MOS sensors.
I will try to get a hold of the data sheet fo Sensorion SGP30 you referenced. I'm still very skeptical of this technology.

I've been using an industrial PID meter and 3rd party lab testing for my VOC measurements. And still I've been mislead by calibration issues. If I could get confidence of MOS technology it would make my task a lot easier and cheaper.

Couple of questions:
With a PID meter I get immediate readings that respond to the environment. Do the MOS sensors respond in the same manor? My impression is that these devices have a much longer settling time.
PID meters can be calibrated with a measured quantity of Isobutylene. What's the procedure for MOS devices and how long does it take? Do the sensor age and need to be replaced?
Do you have any references on the accuracy of these devices? Any testing data compared to PID and GC/MS?

When I refer to TVOC levels I'm refering to total vocs in the environment, not just the vocs that a measuring instrument can detect.
Current recommendations from a number of agencies are:
<200 ng/liter for ideal levels - ~50- 100 ppb
<400 ng/liter for acceptable levels - ~100 - 150 ppb

I'm concerned with
Benzene, Toulene, Ethylenebenzene, Xylene, Terpines, Acetone, Formaldehyde, Acetaldehyde,1,2-Dichloropropane, Propylene, and more. Please excuse spelling.

I'm not concerned about particulates as these are easily handled by particulate filters. VOCs, on the other hand, can be a bear. For the last year or so I've been looking into mitigation strategies.
I"ve seen a lot of marketing hype (PCO, Plasma IONs) but results and real data indicate there are many unknowns. I've found many so called experts lacking in basic fundamentals.
Seems adsorptions technologies and fresh air exchange work, but even with these objective measuring devices are needed to see if progress is being made. And that's why I'm very interested in your experience with MOS devices.

Thanks
Randy

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[HVAC_Marc]

...

I see. I thought you meant there was going to be some magical device that made all this happen. A reporting device could be beneficial IF the end user actually followed up on the reporting.

[rjk_cmh]

For 20 bucks I get a differential pressure switch to hook into my EIM that will send an email when the filter reaches its final pressure drop rating. I can see that the technically minded geeks might want to see the particulate numbers and whatnot, but it's not going to be a common upsell, and I don't see it being installed on 98% of jobs.

[servicefitter]

With a Leeds building they test for 6 different chemicals only one or two you have listed. Leeds is the gold standard for buildings. Just investigate leeds buildings.

[randyf]

With a Leeds building they test for 6 different chemicals only one or two you have listed. Leeds is the gold standard for buildings. Just investigate leeds buildings.

The VOC I listed were increased in my residence (and there were more). I've tested via Gas Chromatography/Mass spec (the gold standard)
The 6 vocs Leeds listed are just generic VOCs that are often raised after new construction. That has nothing to do with over 450 VOCs that can be raised for all sorts of reasons that have nothing to do with new construction.

[technocratic]

I dont mean to be negative, but at what point do you tear your house down, put on a hermetically sealed space suit? I appreciate that you are innovating and it probably has a place in industrial sites (maybe) but to your average home owner? I seriously doubt it. Not only that, but once we alert on a VOC, or other bit of nasty, what is the solution? Tear the house down, and climb into your space suit?

Sent from my SM-N950U using Tapatalk

[kevinsf1]

Slightly off-topic, but has anyone checked out the new Johnson Controls GLAS Thermostat? It's another Smart Thermostat, but it's differentiation over Nest & EcoBee is that it was an IAQ Monitor built in. Doubtful it's anything that a professional might use to scientifically calculate air quality, but might be better than anything else the average homeowner/consumer might use!

[randyf]

I dont mean to be negative, but at what point do you tear your house down, put on a hermetically sealed space suit? I appreciate that you are innovating and it probably has a place in industrial sites (maybe) but to your average home owner? I seriously doubt it. Not only that, but once we alert on a VOC, or other bit of nasty, what is the solution? Tear the house down, and climb into your space suit?

Sent from my SM-N950U using Tapatalk

For the *average* home - I agree. But not all homes are average as I learned the hard way.

I purchased a condo a couple of years ago. Previous owners didn't vacate for a month after initial home inspection. I didn't move in for another 3 months after that.
Immediately after closing I noticed *smells*. I was told these were just residual odors from the excellent cleaning job that the previous owners did before vacating - nothing to worry about. They faded over the next few weeks but didn't go away. I was advised not to worry. A month before I moved in I contacted the home inspection company. They told me all is fine, nothing to worry about. I wanted to believe them. After moving in there were still residual odors.

I didn't know squat about IAQ issues, but quickly learned 2 important points.
1. VOC levels can be accurately measured, relatively inexpensively.
2. There are standards so these measurements can be evaluated.

Shortly after testing I called the home inspection company and told them that they were wrong, that had an issued determined by objective testing. Their response - "Sorry but we don't know anything about IAQ so don't hold us accountable". I then asked them -if you don't know anything about IAQ why did you tell me there was nothing to worry about??They were silent. What really irks me is that they has a list of local IAQ experts that they could have recommended but didn't.

In my case levels were about 700% above maximum acceptable levels and some of the VOCs were of the more objectionable types.
I've got a background in the basic sciences/engineering and research so I studied up. Found a lot of over hyped claims without substantiation. I've tested a number of solutions (mainly in the magic box category).

Fresh air intake, bake outs, ventilation - the old standards do work, but there are still issues.

[breathe easy]

Dr. Iain Walker of Lawrence Berkeley Laboratory has done a very good analysis of low cost IAQ monitors. His findings are summarized in this Powerpoint presentation:

[URL="http://conference2018.resnet.us/data/energymeetings/presentations/RESNET2018_LBL_LowCostMonitors_walker.pdf"]

[breathe easy]

Try this:

http://conference2018.resnet.us/data...ors_walker.pdf

[randyf]

Great paper - thanks.
I"ve been looking for input on this new class of dectector.

[osnabruecker]

If you want to use standart VOC sensor (metal-oxid methode sensor), you must understand that the precision of such sensors aren't very high. Sometimes the sensor could show high level of VOC in the air for H2, H2O or non-VOC gases.

But there are no one another sensor even for 1000$ that could measure VOC more exactly and could exactly measure only VOC.