Particulate Matter

[mweinelt]

Hi,

I want to discuss adding a schema for particule matter sensors. These are usually prefixed with PM follwed by the largest size in ug/m³ that the value contains.

Common sizes are PM2.5 and PM10, which are commonly available in implementations like the Airrohr through the SDS011 sensor. Newer sensors like the SEN5x from Sensirion additionally provide PM1 and PM4 down to 0.3ug/m³.

If we handle this like carbondioxide, then the name would be something like particulate_matter_2_5 for PM2.5. We're currently even rolling with particulate_matter_lte_2_5, but that might be overkill.

No other space seems to have such a value, I grepped for pm and particulate.

[s3lph]

Hi @mweinelt

Thanks for the suggestion, I think it would make a good addition to the schema. I would propose we implement this similar to e.g. the wind or network_traffic sensor type, which also supports multiple properties per sensor. For PM it could look something like this:

{
  # ...
  "sensors": {
    "particulate_matter": [
      {
        "location": "Hackcenter",
        "lastchange": 1756499104,
        "properties": {
          "PM10": {
            "value": 20,
            "unit": "µg/m³"
          },
          "PM2.5": {
            "value": 25,
            "unit": "µg/m³"
          }
        }
      }
    ]
  }
}

What do you think about this?

Furthermore, to get started on the spec, do you know:

• What units are commonly used to measure PM? From a quick research I came across µg/m³ being the most common.
• Which particle sizes are commonly used? From your initial comment I'm reading PM10, PM4, PM2.5, PM1 and PM0.3 being common enough to warrant inclusion in the schema. Are you aware of any other sizes that we'd need to account for? Nothing is preventing endpoints from adding their own, but values not defined in the schema may be ignored by clients.

[s3lph]

I just realized that our space actually has a PM sensor, so I went ahead and implemented my proposal above in our SpaceAPI endpoint:

$ curl -s https://spaceapi.kabelsalat.ch | jq .sensors.particulate_matter
[
  {
    "location": "Hackspace",
    "properties": {
      "PM10": {
        "value": 8.15,
        "unit": "µg/m³"
      },
      "PM2.5": {
        "value": 2.42,
        "unit": "µg/m³"
      }
    }
  }
]

@SpaceApi/core any thoughts from your side?