core/homeassistant/components/airgradient/icons.json

{
  "entity": {
    "sensor": {
      "total_volatile_organic_component_index": {
        "default": "mdi:molecule"
      },
      "nitrogen_index": {
        "default": "mdi:molecule"
      },
      "pm003_count": {
        "default": "mdi:blur"
      }
    }
  }
}