The table below describes the fields found in CSV files recorded by PurpleAir sensors to microSD cards.
SD Data is recorded using different field names than those used in the PurpleAIr API. You can examine the API documentation to see queryable fields from the API.
If you experience any problems with SD data collection, including missing data or wrong dates, read the information in our SD Card Logging and Troubleshooting article.
When collecting SD data, we recommend using the PurpleAir Utility’s SD Data Tool. It can merge data into a single file and recover data found in log files.
Sensor Information Columns
| Column Name | Description |
|---|---|
| UTCDateTime | The time when this row of data was recorded. Derived from the Real-Time Clock and synced with NTP where possible. This is in the format YYYY/MM/DDTHH:MM:SSz and uses UTC as the timezone. |
| mac_address | The sensor’s Device ID. This is identical to the sensor’s MAC address, except that leading 0’s are omitted in each Octet. For example, device ID 8:3a:8d:b:a4:fd would correspond to the MAC address 08:3a:8d:0b:a4:fd. |
| firmware_ver | Firmware version of the control board. |
| hardware | Hardware type the control board has detected. |
| uptime | Firmware uptime in seconds. Rebooting the sensor will reset this to 0. |
| rssi | WiFi signal strength in dBm. |
| mem | Free HEAP memory on the control board. |
| adc | The voltage reading on the analog input of the control board. |
Environmental Data Columns
Temperature and humidity data reflect conditions in the sensor’s housing and do not always match ambient readings. However, corrections are available to better match ambient conditions. Further information can be found in A Note on Temperature and Humidity.
| Column Name | Description |
|---|---|
| current_temp_f | Current temperature in Fahrenheit. This is taken directly from the sensor without applying a correction. |
| current_humidity | Current Humidity in %. This is taken directly from the sensor without applying a correction. |
| current_dewpoint_f | Calculated dew point in Fahrenheit. Calculated using uncorrected temperature. |
| pressure | Current pressure in millibars. |
| gas | Bosch BSEC IAQ when BME680 gas sensor is present (FIRMWARE 4.10 and up). These readings are experimental. |
Air Quality Data Columns
All air quality data columns represent data from either laser counter A or laser counter B. Columns with “_b” at the end represent data from channel B. If “_b” is not at the end of an air quality data column, it represents data from channel A.
Further information relating to some of the air quality data columns can be found in:
Air Quality Channel A Columns
| Column Name | Description |
|---|---|
| pm1_0_cf_1 | Channel A CF=1 PM1.0 particulate mass in ug/m3. |
| pm2_5_cf_1 | Channel A CF=1 PM2.5 particulate mass in ug/m3. |
| pm10_0_cf_1 | Channel A CF=1 PM10.0 particulate mass in ug/m3. |
| pm1_0_atm | Channel A ATM PM1.0 particulate mass in ug/m3. |
| pm2_5_atm | Channel A ATM PM2.5 particulate mass in ug/m3. |
| pm10_0_atm | Channel A ATM PM10.0 particulate mass in ug/m3. |
| pm2.5_aqi_cf_1 | Channel A US EPA PM2.5 AQI calculated using pm2_5_cf_1. |
| pm2.5_aqi_atm | Channel A US EPA PM2.5 AQI calculated using pm2_5_atm. |
| p_0_3_um | Channel A 0.3-micrometer particle counts per deciliter of air. |
| p_0_5_um | Channel A 0.5-micrometer particle counts per deciliter of air. |
| p_1_0_um | Channel A 1.0-micrometer particle counts per deciliter of air. |
| p_2_5_um | Channel A 2.5-micrometer particle counts per deciliter of air. |
| p_5_0_um | Channel A 5.0-micrometer particle counts per deciliter of air. |
| p_10_0_um | Channel A 10.0-micrometer particle counts per deciliter of air. |
Air Quality Channel B Columns
| Column Name | Description |
|---|---|
| pm1_0_cf_1_b | Channel B CF=1 PM1.0 particulate mass in ug/m3. |
| pm2_5_cf_1_b | Channel B CF=1 PM2.5 particulate mass in ug/m3. |
| pm10_0_cf_1_b | Channel B CF=1 PM10.0 particulate mass in ug/m3. |
| pm1_0_atm_b | Channel B ATM PM1.0 particulate mass in ug/m3. |
| pm2_5_atm_b | Channel B ATM PM2.5 particulate mass in ug/m3. |
| pm10_0_atm_b | Channel B ATM PM10.0 particulate mass in ug/m3. |
| pm2.5_aqi_cf_1_b | Channel B US EPA PM2.5 AQI calculated using pm2_5_cf_1_b. |
| pm2.5_aqi_atm_b | Channel B US EPA PM2.5 AQI calculated using pm2_5_atm_b. |
| p_0_3_um_b | Channel B 0.3 micrometer particle counts per deciliter of air. |
| p_0_5_um_b | Channel B 0.5 micrometer particle counts per deciliter of air. |
| p_1_0_um_b | Channel B 1.0 micrometer particle counts per deciliter of air. |
| p_2_5_um_b | Channel B 2.5 micrometer particle counts per deciliter of air. |
| p_5_0_um_b | Channel B 5.0 micrometer particle counts per deciliter of air. |
| p_10_0_um_b | Channel B 10.0 micrometer particle counts per deciliter of air. |
Once the SD card in a PurpleAir device is full, the sensor will not overwrite previous data. Instead, the sensor will stop reporting. A 16 GB SD card can hold around two years of data.