The following items written in bold are the headers of the SD card data that PurpleAir sensors log. What follows are their descriptions.
UTCDateTime : The Date and time derived from the Real-Time Clock and synced with NTP where possible (in UTC).
mac_address : The Date and time derived from the Real-Time Clock and synced with NTP where possible (in UTC).
firmware_ver : Firmware version of the control board.
hardware : Hardware type the control board has detected.
current_temp_f : Current temperature in Fahrenheit.
current_humidity : Current Humidity in %.
current_dewpoint_f : Calculated dew point in Fahrenheit.
pressure : Current pressure in millibars.
adc : The voltage reading on the analog input of the control board.
mem : Free HEAP memory on the control board.
rssi : WiFi signal strength in dBm.
uptime : Firmware uptime in seconds.
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 CF=1 calculated US EPA PM2.5 AQI.
pm2.5_aqi_atm : Channel A ATM calculated US EPA PM2.5 AQI.
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.
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 CF=1 calculated US EPA PM2.5 AQI.
pm2.5_aqi_atm_b : Channel B ATM calculated US EPA PM2.5 AQI.
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.
gas : Bosch BSEC IAQ when BME680 gas sensor is present (FIRMWARE 4.10 and up).
Every PA-II, PA-II-SD, and PA-II-FLEX sensor contains two laser counters labeled channel A and channel B.
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.