While working from home can provide many benefits there are also some new challenges that come with it. Many standards ensure the healthiness of office workspaces, so let's attempt to also take care of these at home:

  • As a maker/hacker/gamer/online-content-prosumer you probably already have a comfy and ergonomic setup
  • Good lighting is important to stay awake and not get SAD (Seasonal Affective Disorder) while staying indoors. Office lighting in Germany has to be >500lx. I went with a few COBs at about 70W, dimmable, 3000K, high CRI.
  • But what about ventilation?

CO2 as a guide for ventilation

There are some conflicting studies about the impact of CO2 levels on cognitive abilities. Some found a significant decrease in performance at levels starting at about twice the current outside CO2 levels while others couldn't recreate these. Since there are few CO2 sources besides humans in indoor environments it still seemed like a good approach to me to use this to ventilate sufficiently and be on the safe side in case the studies that found a correlation were right.

An indication of CO2 also makes sense in the office or just in general when meeting people because there will be a strong correlation between these levels and how much potentially contagious aerosol is in the air.

In general indoor CO2 levels probably rise faster than you expect. Small rooms have to be vented hourly. Even if we leave all the doors open in our 100m^2 apartment with 2 rather small humans in it levels are above 1000ppm in the morning after venting down to 400ppm in the evening. I don't even want to know how high they rose in my tiny dorm room...

Some more convenience for calls

Since I was already hacking together a wfh device I also wanted to take care of another thing: Convenient muting and unmuting. Sure, there's a shortcut or you could just click the button, but I like to have things that I do a lot perfectly optimized. It also keeps the device in sight and makes you notice venting notifications.

The device

It was just a hacky weekend project using what I had laying around for completely unrelated projects, but it turned out quite nice and very usable. I used a Digispark to read the sensor, change the color of the dual color LED and send the shortcut for muting when I press the button.

The housing is 3D-printed and diffuses the glow of the dual color LED nicely. It also made me discover how silicone feet can improve the haptics of my prints in general. The CO2 sensor vents to the back so you can't breath on it directly.

I wanted the notification to be subtle so it doesn't break my focus when I'm in the flow, so no pop-ups, vibration or sound. I actually have another commercial sensor but I don't want to read values and compare them against thresholds in my head when the device could take care of that for me. The bright LED takes care of the notifications really well. It's visible in bright light and looks neat in the dark.

Here's a video describing the Project:

CO2 sensors

I used a "real" CO2 sensor that works by measuring the IR absorption of CO2 present in the air. The end of the video shows the glow of the small lamp in the sensor that is used to generate light with long wavelength components. The light is then measured by two sensors, one tuned to CO2 absorption and one for reference. These sensors are however quite expensive. (around 20 bucks from china, twice as much from local distributors, even more for branded products)

VOC sensors are cheaper and can output "equivalent CO2", essentially just multiplying the measured volatile organic compounds by the average proportion of exhaled VOCs to CO2. These could be confused by your furniture, a strong drink and many other sources. They just make you vent more often then, so no issue. Packaging is small enough for any device.

There are also some nice photoacoustic CO2 sensors that come in a smaller package and work by agitating the CO2 molecules with infrared light and measuring...

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