CoronaAir

CoronaAir

It has always been important to stay healthy, since the corona pandemic even more so. To make sure of that, we have to refresh the air in our rooms regularly. Many of the solutions in the market are quite expensive, up to a few hundred euros for a simple “CO2 Signal”. Commonly, they offer three lights:

But what do these lights mean? How long is the light red? Is it becoming red for a few seconds or is it red since hours? How bad is the air really? Is it a bit above the limit or is it beyond good and evil? Nobody knows. What means yellow? Should I open the windows now or is it save to ignore it?

So, the idea of the project is, to create a visualization of time and air quality with a cheap sensor. You don’t need an expensive CO2 sensor, because you don’t measure the exhaust of non-human things. In a room there are only humans, or a few pets, with less impact on air quality. A VOC (Volatile Organic Objects) sensor measures the air bound organic particles and gives you a quantitative measurement of them. This can be interpreted as eCO2 (equivalent CO2), what’s enough for estimating the air quality. eCO2 is calculated, based on the typical exhaust of CO2 of humans on a specific TVOC (Total VOC) level. If you have something else in your living room (e.g. a gasoline generator), the calculated CO2 value is useless, so please be very careful with such sensors. It is made for measuring the exhaust of human organic particles after all.

Also, it can be problematic with other occurring sources of organic particles like in a kitchen, crafting rooms and toilets. The measurement will be inaccurate believe me; I speak from experience 😉.

What we want

We want an understandable visualization of air quality. Why? Well, you can open or close a window, true or false, to say: “Em, you may open your windows, it would be good if you do it, but you don’t have to do it right now” is useless and unsettles the user. A yellow light is such a non-understandable message. You need a clear message:

To open or not to open, that is the question!

You will receive a message with a clear request: Open the window or close it. Nothing else. If you ignore it, well it’s your loss, right?

The next point to consider is, the visualization. Nobody is interested into ppm, mg/cm3 or something else they don’t even fathom (of course, if you are not a nerd like we are 😊 😊 😊). You want to know how bad or, good the air quality is. We send a periodic diagram with a red or green filled graph via a Telegram chatbot. You´ll see with a quick look: Well, my refreshing performance is good, or oh snap! I’ve forgotten to open the windows! With the timestamp you can see when you have lost control and work on your skills. It’s a good way of self-control and creates the capability to compare to others and learn from them.

But why do we use a chat-bot, and not a sneaky screen where everyone can read the messages? Cause nobody is looking on a small screen in a room. You must walk to it and pay attention when you do not forget to check it regularly that is. Also, you can be warned by an acoustic or visual signal. But that interrupts activity of all people in the room and is not needed. It is only one person necessary for opening and closing windows.

But how can we tell only one person without interrupting the others? The person should be able to have access to little, mobile screen with internet capabilities and a non-intrusive notification system. Well, smartphones cover these needs, don’t they?

How it works

You will place a little sensor in every room, it should be placed on a central spot, where the air is circulating. On the door you pin a QR-code that identifies the sensor. If you enter the room, and are responsible for ventilation, you take a picture of it and send it the bot. The bot will automatically subscribe you and inform about the stats of the room. If you leave, you write a /logout command and will be unsubscribed. You can be only subscribed to one room. If you subscribe to another room, you will be automatically unsubscribed from the old one.

For the interested and technic nerds

The sensor is communicating over a REST-API with a database interface server. This instance is storing the informations in a database and identifying each entry with a unique key. The key is the MAC-address of the sensor in a numeric format and must be printed as a qr-code. Scanning the code will start a process on the main instance and send messaging as referred in the sections above. As a main instance a Raspberry PI 3 will sufficient. The main instance is gathering the needed information from the database. The REST-API server and the main instance is running on the same hardware.