Designed for continuous outdoor deployment across real-world environments.

A-I

Air Quality Index (AQI) — A standardised scale used to communicate how polluted the air is at a given moment. Different countries use different AQI scales (the UK uses DAQI; the US uses its own EPA scale). Persium data can be mapped to multiple index frameworks depending on the reporting context.

Ambient monitoring — Measurement of pollutants in the open air, as opposed to indoor or source-specific monitoring. Persium's outdoor sensors are designed for ambient deployment.

Background concentration — The baseline level of a pollutant present in the air independent of local sources. Understanding background levels helps distinguish the contribution of specific activities or infrastructure.

Black carbon (BC) — Fine particulate matter produced by incomplete combustion, particularly from diesel engines. A useful indicator of traffic-related pollution. Measured by Persium sensors in applicable deployments.

Calibration — The process of adjusting sensor readings against a reference instrument to improve accuracy. Persium sensors are calibrated before deployment and monitored continuously for drift.

CO₂ (carbon dioxide) — A greenhouse gas and indoor air quality indicator. Elevated CO₂ in enclosed spaces signals inadequate ventilation. Measured by Persium in indoor deployments.

DAQI (Daily Air Quality Index) — The UK's air quality reporting scale, running from 1 (low) to 10 (very high). Used by DEFRA and local authorities to communicate public health risk. Persium data can be presented in DAQI format.

Digital twin — A virtual model of a physical environment, updated with real-time data. Persium's platform can function as a digital twin layer for a city district, building, or transport network, allowing simulation of pollution scenarios.

Electrochemical sensor — A sensor type that detects gas concentrations via chemical reactions. Used in Persium sensors for certain gaseous pollutants including NO₂, O₃, and CO.

Fugitive emissions — Uncontrolled releases of pollutants from sources such as construction sites, quarries, or port operations. Persium is used to detect and attribute fugitive emission events.

Hyper-local monitoring — Air quality measurement at a spatial resolution finer than traditional reference networks. Persium's sensor networks are designed for hyper-local deployment — capturing variation at street, building, or even room level.

IAQ (Indoor Air Quality) — The condition of air within and around buildings. IAQ is measured across parameters including PM2.5, CO₂, VOCs, temperature, and humidity. Relevant to WELL and LEED certifications, occupant health, and productivity.

IoT (Internet of Things) — The network of physical devices that collect and transmit data via the internet. Persium sensors are IoT-enabled, transmitting data in real time to the cloud platform.

L–P

LEED (Leadership in Energy and Environmental Design) — A globally recognised green building certification. Indoor air quality data — including PM2.5, CO₂, and VOCs — is relevant to several LEED credits. Persium's platform can support the data requirements for relevant credits.


LEZ / ULEZ (Low Emission Zone / Ultra Low Emission Zone) — Designated areas where vehicle access is restricted based on emission standards. Air quality monitoring data is used to design, justify, and evaluate these zones. Persium has supported LEZ planning in Westminster and other boroughs.


LiDAR — Light Detection and Ranging. A remote sensing technology sometimes used alongside air quality monitoring for spatial analysis of pollution dispersion. Not a Persium sensor type, but relevant context for multi-modal environmental data projects.


Mobile monitoring — Air quality measurement using sensors mounted on moving platforms such as vehicles, vessels, or drones. Persium sensors have been deployed on buses and river vessels, enabling dynamic spatial coverage.


NO₂ (nitrogen dioxide) — A gaseous pollutant primarily produced by combustion, particularly from road traffic and industrial sources. A key regulated pollutant under WHO and EU standards. Measured by Persium sensors.


NOx (nitrogen oxides) — The collective term for nitric oxide (NO) and nitrogen dioxide (NO₂). A precursor to secondary pollutants including ozone and fine particulate matter.


O₃ (ozone) — A secondary pollutant formed when NOx and volatile organic compounds react in sunlight. Elevated ground-level ozone causes respiratory harm. Measured by Persium in applicable configurations.


Optical particle counter (OPC) — A sensor type that counts and sizes airborne particles using light scattering. Used in Persium sensors for particulate matter measurement.


PM1, PM2.5, PM10 — Particulate matter categories defined by particle diameter (in micrometres). PM2.5 and PM10 are subject to WHO and national air quality guidelines. PM2.5 is the most health-critical, penetrating deep into the lungs. All three are measured by Persium's Pod and Pill.


Persium Pill — Persium's compact indoor sensor, measuring 21 environmental parameters including PM2.5, CO₂, VOCs, temperature, and humidity. Designed for indoor deployment in buildings, transport assets, and enclosed infrastructure.


Persium Pod — Persium's outdoor environmental sensor, measuring 31 parameters. Designed for urban, industrial, and transport environments. Can be mounted on street furniture, vehicles, or buildings.

R-Z

Real-time monitoring — Continuous measurement and transmission of air quality data as it is generated. Persium sensors transmit data in real time, enabling immediate detection of pollution events and live dashboard views.


Reference station — A fixed, high-accuracy monitoring station used to establish official air quality readings for regulatory purposes. Typically spaced kilometres apart. Persium networks complement reference stations by providing spatial density between them.


Sensor fusion — Combining data from multiple sensor types or sources to improve overall data quality and coverage. Persium's platform applies sensor fusion techniques to produce more reliable pollution maps.


Source apportionment — The process of identifying and quantifying the contribution of different pollution sources (traffic, industry, biomass burning, etc.) to observed concentrations. Persium data can support source apportionment analysis.


UFP (Ultrafine Particles) — Particles smaller than 0.1 micrometres in diameter. Not yet widely regulated but associated with significant health effects. Measured by Persium in selected configurations.


VOCs (Volatile Organic Compounds) — A broad class of gases emitted from fuels, solvents, vegetation, and building materials. Some VOCs are directly harmful; others contribute to the formation of ground-level ozone and secondary PM. Measured by Persium's sensors.


WBGT (Wet Bulb Globe Temperature) — A composite heat stress index that accounts for temperature, humidity, radiant heat, and wind speed. Relevant to outdoor worker safety and sporting events. Persium sensor parameters can be used to calculate WBGT in applicable deployments.


WELL Building Standard — A performance-based certification focused on occupant health and wellbeing. Air quality is a core feature of WELL, covering parameters including PM2.5, CO₂, VOCs, and ventilation. Persium's indoor monitoring data supports WELL assessment.


WHO Air Quality Guidelines — The World Health Organisation's recommended limits for key air pollutants, updated in 2021. Stricter than most national standards. Used as a reference point for assessing the health impact of air quality data, including Persium deployments.