Adds documentation for the proposed AirVisual sensor platform

source/_components/sensor.airvisual.markdown

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+---
+layout: page
+title: "AirVisual"
+description: "Instructions on how to use AirVisual data within Home Assistant"
+date: 2017-09-06 12:15
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: airvisual.jpg
+ha_category: Health
+ha_release: 0.53
+ha_iot_class: "Cloud Polling"
+---
+
+The `airvisual` sensor platform queries the [AirVisual](https://airvisual.com/) API for air quality
+data on the nearest city to a latitude and longitude. The resulting information
+creates sensors for the Air Quality Index (AQI), the human-friendly air quality
+level, and the main pollutant of that area. Sensors that confirm to either/both
+the [U.S. and Chinese air quality standards](http://www.clm.com/publication.cfm?ID=366) can be created.
+
+This platform requires an AirVisual API key, which can be obtained [here](https://airvisual.com/api). Note
+that the platform was designed using the "Community" package; the "Startup"
+and "Enterprise" package keys should continue to function, but actual results
+may vary (or not work at all).
+
+<p class='note warning'>
+The "Community" API key is limited to 10,000 calls per month. In order to leave
+a buffer, the `airvisual` platform queries the API every 10 minutes.
+</p>
+
+## {% linkable_title Configuring the Platform %}
+
+To enable this platform, add the following lines to your `configuration.yaml`
+file:
+
+```yaml
+sensor:
+  - platform: airvisual
+    api_key: abc123
+    monitored_conditions:
+      - us
+      - cn
+    latitude: 42.81212
+    longitude: 108.12422
+    radius: 500
+```
+
+Configuration variables:
+
+- **api_key** (*Required*): your AirVisual API key
+- **monitored_conditions** (*Required*): the air quality standard(s) to use
+(`us` for U.S., `cn` for Chinese)
+- **latitude** (*Optional*): the latitude to monitor; if excluded, the latitude
+defined in `configuration.yaml` will be used
+- **longitude** (*Optional*): the longitude to monitor; if excluded, the longitude
+defined in `configuration.yaml` will be used
+- **radius** (*Optional*): the radius (in meters) around the latitude/longitude to
+search for the nearest city; defaults to `1000`
+
+## {% linkable_title Sensor Types %}
+
+When configured, the platform will create three sensors for each configured
+air quality standard:
+
+### Air Quality Index
+
+**Description:** This sensor displays a numeric air quality index (AQI), a metric
+for the overall "health" of the air.
+
+**Example Sensor Name:** `sensor.chinese_air_quality_index`
+
+**Example Sensor Value:** `32`
+
+**Explanation:**
+
+AQI | Status | Description
+------- | :----------------: | ----------
+0 - 50  | **Good** | Air quality is considered satisfactory, and air pollution poses little or no risk
+51 - 100  | **Moderate** | Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution
+101 - 150 | **Unhealthy for Sensitive Groups** | Members of sensitive groups may experience health effects. The general public is not likely to be affected
+151 - 200 | **Unhealthy** | Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects
+201 - 300 | **Very unhealthy** | Health warnings of emergency conditions. The entire population is more likely to be affected
+301+ | **Hazardous** | Health alert: everyone may experience more serious health effects
+
+### Air Polution Level
+
+**Description:** This sensor displays the associated `Status` (from the above
+table) for the current AQI.
+
+**Sample Sensor Name:** `sensor.us_air_pollution_level`
+
+**Example Sensor Value:** `Moderate`
+
+### Main Pollutant
+
+**Description:** This sensor displays the pollutant whose value is currently
+highest.
+
+**Sample Sensor Name:** `sensor.us_main_pollutant`
+
+**Example Sensor Value:** `PM2.5`
+
+**Explanation:**
+
+Pollutant | Symbol | More Info
+------- | :----------------: | ----------
+Particulate (<= 2.5 μm) | PM2.5 | [EPA: Particulate Matter (PM) Pollution ](https://www.epa.gov/pm-pollution)
+Particulate (<= 10 μm) | PM10 | [EPA: Particulate Matter (PM) Pollution ](https://www.epa.gov/pm-pollution)
+Ozone | O | [EPA: Ozone Pollution](https://www.epa.gov/ozone-pollution)
+Sulpher Dioxide | SO2 | [EPA: Sulfur Dioxide (SO2) Pollution](https://www.epa.gov/so2-pollution)
+Carbon Monoxide | CO | [EPA: Carbon Monoxide (CO) Pollution in Outdoor Air](https://www.epa.gov/co-pollution)