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I thought measuring air quality was like measuring current or voltage. You read what it says on the multimeter and the voltage is too high or too low. I was horribly mistaken. Air quality is a different matter. I should have known because I am somewhat familiar with the legislation on welding fumes. The legislation states how many mg/m3 the welder may be exposed to in a maximum of 8 hours. But that depends on many factors, such as the type of exhaust and filter system used, how the welder uses the equipment, how long he or she is welding for, ventilation of the space in general, etc.
To answer these questions, I looked up "ohm's law for air quality". There is a lot of information on the internet. The most interesting information I found was on the website of the RIVM. The RIVM is the National Institute for Public Health and the Environment here in the Netherlands. It turns out that many makers are already measuring air quality and the RIVM is advising and working with them. An interesting option is that you can place a sensor for a month in an official and professional measuring facility of the RIVM. After that month, the sensor is returned to you, along with the official data measured during that period. With this data, you can calibrate your own sensor. Maybe I will do that one, but other information makes me think that this is not the most important thing. Below is a map of the data of the makers and the official map.
Most interesting, however, is the information on air quality. This dutch article in a newspaper (Volkskrant) made it clear to me that I would not find "the law of ohm for air quality". The article described how 23 calibrated air quality meters had been placed in 23 houses. It showed that it was mainly behaviour that determined air quality inside and that much is still unclear. Besides measuring, the owners also kept a diary. When the owner's irons, cook or light candles the charts show a sharp increase in particulate matter. According to the expert, the peak during ironing is probably caused by lime particles from the steam iron. If that gets into the lungs it will probably dissolve and not harm the body but the expert cannot guarantee this. There are many rules for ventilating houses, but not for extractor hoods. Cooking on gas without a good extractor hood is strongly advised against according to the same expert. Here I can make a link with welding because welding without extraction is also not recommended. Since I have an ESDK set at my disposal, I naturally had to test whether a candle did indeed cause a rise.
The sensor's datasheet indicates a tolerance of +/- 10ug/m^3 and I have not had the sensor calibrated at RIVM. Nevertheless, I do not think that my health was at risk with this measurement. I have the following reasons for this:
- The values are still below the official maximum average values of 40 ug/m3 per year.
- I have only been exposed to these values for a short time, much longer periods to much lower values
- The distance from the candle to the sensor is short, I was about a factor of 5 to 10 further away. Like welding fumes, the intensity probably decreases by a factor of 25 to 100 or so when you are further away from the source.
Nevertheless, I am now aware that it is not wise to fill my entire room with burning candles. So the ESDK kit and air quality sensors should not be used so much as a multimeter. However, it is probably a suitable instrument for creating awareness. Better awareness can result in different behaviour. Perhaps it is more important to know that the extractor should be turned on before it starts to smell and less important to know exactly how many ug/m3 the extractor removes.
Experimenting with this ESDK kit is made very simple. After experimenting for a couple of months and searching for information my project plan looks as follows. First I want to test the system with a welding fume. It is possible to store the information in a CSV, so this option I need to use because I will not have access to the internet when I'm measuring this data. After measuring this behaviour for some time, the values must be translated into behaviour. Based on this result I will adjust the display so that it gives an indication of what the welder should do. Switch on the exhaust or position it better. So it is time to test my programming skills, which will be challenging for me. The intention is to finish this within a couple of weeks and share the result here again also.