Table 7 Description of the variables and attributes of the “QUANT_SensorSystems_hourly.csv”.

time

The time format is DD/MM/YYYY HH: mm. The measurement period covered in this file extends from 10 Dec 2019 to 31 Nov 2022.

date

location

Sites where the measurements were taken in the UK. Alternative values:

string

- MAQS: Manchester (lat 53.444222 N, long −2.214417E);

- LAQS: London (lat 51.449694 N, long −0.037389E);

- YoFi: York (lat 53.951917 N, long -1.075861E).

instrument

Sensor system’s name. Alternative values for the Main QUANT study: Ari063, Ari078, Ari086, Ari093; AQM388, AQM389, AQM390, AQM391; AQY872, AQY873, AQY874, AQY875; PA1, PA2, PA3, PA4, PA5, PA6, PA7, PA8, PA9, PA10;Zep188, Zep309, Zep311, Zep344;

string

Alternative values for the Wider Participation Study: AQM1, AQM2, AQM3; AP1, AP2, AP3; Atm2, Atm1; IMB2, IMB1; Mod1, Mod2, Mod3; NS1, NS2, NS3; Poll1, Poll2; Prax1, Prax2; SA1, SA2, SA3.

sensornumber

Relates to the history of the sensing element, and can take integer values between 1 and 3. If the sensor has never been replaced, it’ll take a value of “1”.

int16

version

It describes the data product. Alternative values:

string

- out-of-box: data product produced by default by the manufacturer;

- cal1: first corrected/calibrated data product;

- cal2: second corrected/calibrated product;.

A special case is the PurpleAir sensors, which can only take the alternative atmospheric and indoor which are the default data products from that company. See²⁷ for more details.

measurand

Short names for the air pollutants (or meteorological variables) included in the files. Alternative values are: NO, NO2, O3, PM2.5, PM10, Pressure, RelHumidity and Temperature.

string

measurement

Measurement values. Units for the air pollutants: for NO, NO2 and O3: ppb; for PM1, PM2.5, PM10: ug/m³; Units for meteorological variables: Pressure: hectopascal (hPa); RelHumidity: percentage (%); Temperature: Kelvin (K);

float64

flag

Quality flag indicator. Alternative values are:

string

○ None: the data can be considered reliable without specific reservations;

○ Info: additional information, it does not necessarily indicate a problem.

○ Warning: data may have minor issues, but are not serious enough to invalidate the data;

○ Error: the data has significant issues that affect its reliability.

flagreason

It can take integer values between 1 and 4 for most companies. For others, this can range up to 16 (see *special cases).

string

For the general case, it can take these string values:

○ None: no issues;

○ Retrospectively_collected: the data wasn’t collected right after it was generated;

○ Power_problem: power outage at the site.

*special cases: some companies offer extra metadata. For comprehensive details follow the links below:

• Environmental Instruments: https://rb.gy/c1qs6t;

• Kunak: https://rb.gy/qoo5z3;