Hi @Cjheng 

This is an interesting question, thanks for creating a posting about it.

To help answer this, we first need to provide some context to what Volatile Organic Compounds (VOCs) are, the number of gasses include and how the sensors across Air Purifiers account for their readings.

VOCs are made up from an extremely large group of gasses, over 5,000 of which are expelled by; breathing, cooking, bodily functions, perfumes, deodorants, paints, and cleaning material, as well as other sources both in the home and outside. Due to the number of gaseous sources, a fixed PPM (Parts per million) for every in-home environment cannot be automatically generated. Instead, the onboard sensors use a baseline PPM and reacts to changes in the local environment using a logic algorithm (Automatic Baseline Correction). This algorithm eliminates any sensor drift and drives the sensor to quickly reduce the baseline when a time of low measurement is sensed.

Using the above baseline and detection method, we can quickly identify peaks in the sensor readings and attribute this to the presence of VOCs. The greater the peak, the greater the Dyson Air Quality Information (AQI) shown.

The baseline is created by on onboard VOC sensor monitors and provides a CO2 equivalent in PPM.

Read more about overall VOC sensor capabilities here - (VOC Sensor Capabilities and Limitations - Application Note - BAPI (bapihvac.com))

Thanks, 

Stuart

Thanks Stuart.  It certainly goes past my head. Very technical concepts to grasp in the application note. Let me try here after reading it over a few times.  Assuming that the baseline of 450 ppm is adopted, reason being that there are oxidising gases which are not measured by the sensor, can we deduce therefore that there has to be a variation from the 450 ppm baseline for each of the levels in Dyson. What is the variation then from the baseline for each level ?  

Stuart,  having done a little more research and reading the BAPI paper, and considering that not all gases are captured by sensor and there are limitations to it, I do understand that a fixed ppm cannot be automatically generated as you had suggested, I do have two following questions then: 

1.what is the range of the CO2 PPM equivalent for this sensor ?

2.what is the guiding CO2 PPM limits for each of the 0-9+ levels displayed on the Dyson machine ?

Kind regards.

@Cjheng as an owner as welI, I really struggle to see how we’d all benefit from know this.

For me, getting a better understanding of how the sensors work has been great and has helped me understand my machine a little more. But the follow up questions you’ve asked have gone beyond that. It sounds like your trying to create a research paper or something. 

Do you really think Dyson is going to share how they programme their machines? i’d think that would be secret…

David.

Not writing a research paper.  My follow up questions come about from just reading the application note from BAPI to have a better understanding. I wanted to have a certain level of comfort to know what amounts of PPM translates to for eg. a fair amount of VOC in the 4 level reading because I have a room which has the VOC in the 4 level for a long time of 6 months since. Btw,  I have come across some building standards where there are stipulated standards of VOC levels.  Had my room registered in the 0-3 level , I wouldn't bother checking the VOC PPM range really.  But because it is high in 4 and 5, I needed to find out what that equivalent PPM range is. Why do you think that would be secret ?  

By what yardstick is the good, fair, and poor grades measured against ? There has to be a benchmark , you agree ?

I agree that there should be a benchmark, but that is already shown in the app surly. It is just in the app we are shown this in colours. Green is low, red is high. 

If you are seeing a spike that is going into that red, then to me it says something in your room is doing this and not an issue with the Apps benchmarking. 

My VOC reading has spike to moderate and even high in the last few months, this has been down to me painting or having the window open.. 

Doing some research, even my local government site doesn't provide their benchmarking for individual air quality.

I think your barking up the wrong tree here. 

David.

Hey @Cjheng I have to agree with David.

I really don’t think Dyson would share this information or really be obligated to. 

@Stuart has created a number of articles in the community to help us understand the graphs. I’d check these out.

Explanation of the pollutant levels and colours on the graph | Dyson Community 

Viewing your machine's air quality graphs | Dyson Community

Hope this helps :)

 @D.Taylor I’ve just figured out why I get notified when you leave a comment. I’m one of your followers.

Thanks for the sharings

I bought a new large roller blind for my bedroom. Immediately my VOC readings went up on my air purifier The smell was strong from the blind, it has lessened but is still detectable to my nose. The VOC readings continue to show in the Fair range. But I feel a bit off and tired in a way that is unusual. I paid a lot for the blind, almost as much as the Dyson air purifier!! and my air purifier app suggested using the auto setting which is probably worth trying next. One question I have as I get ready to complain to the blind manufacturers is how to access my history of readings? I need to find that, to show them what the blind is doing.